User Guide UG206. Rev. No. Revision Details Date Prepared By Checked By. 02 Add CRC calculations 16 June 2004 A. Lustig-Picus D.

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1 AQBISS TM UNIVERSAL ENCODER INTERFACE User Guide UG206 COPYRIGHT Netzer Precision Motion Sensors Ltd. Changes are periodically made to the information contained in this guide. The changes are published as release notes and will be incorporated into future revisions of this guide. No part of this guide may be reproduced in any form without permission in writing from Netzer Precision Motion Sensors. TRADEMARKS Netzer Precision Motion Sensors, Netzer Precision, and AqBiSS are trademarks of Netzer Precision Motion Sensors Ltd. BiSS is a trademark of the IC-Haus company. ActiveX ComPort is a trademark of the ActiveXperts company. *The names of actual companies and products mentioned herein may be the trademarks of their respective owners. NOTICE Information deemed to be correct at time of publishing. Netzer Precision Motion Sensors reserves the right to change specifications without notice. Netzer Precision Motion Sensors is not responsible for incidental, consequential, or special damages of any kind in connection with this document. Revision History Rev. No. Revision Details Date Prepared By Checked By 01 Initial document. 1 April 2004 S. Guez E Kugushev D. Bar-On 02 Add CRC calculations 16 June 2004 A. Lustig-Picus D. Bar-On Netzer Precision Motion Sensors Ltd. Teradion Industrial Park, POB 1359, D.N. Misgav, Israel Tel: +972 (4) Fax: +972 (4) Web site:

2 Contents 1. Introduction In This Document Terminology References 8 2. AqBiSS AqBI and BiSS Universal Interface for Electric Encoders 9 3. Using AqBiSS with Absolute Netzer AqBiSS Electric Encoders Reading the Absolute Position Finding the Initial Absolute Position Using Only the BiSS for Position Reading Using BiSS Together with AqB for Position Reading Using AqBiSS with Incremental Netzer AqBiSS Electric Encoders Using BiSS Alone for Position Reading Initialization Updating the Actual Position Incrementally Using AqBI for Position Reading How to Work with Netzer AqBiSS Electric Encoders Incremental AqBiSS Electric Encoders Using AqBI Alone Using BiSS Alone Absolute Electric Encoders Using BiSS Alone Using AqB + BiSS Interface to Controller (Closed Loop) Evaluation Kit (Open Loop) Software Interface Contents Verifying Communication Detailed Description of the AqBiSS Interface AqBI Channel A & B Signals and Quadrature Up Down Counting Index Signal BiSS Channel 24 Netzer Precision Motion Sensors Page 2 of 68

3 Advantages of BiSS BiSS Specification BiSS Message Formats Overview of Sensor Mode Overview of Register Mode Communication Modes Timing Address Mapping Functional Registers Encoder System Parameters Encoder Operation Mode Switch Commands Encoder Setup Data Encoder Resolution Code Encoder Functional Parameters Rotary Encoder Functional Parameters Linear Encoder Functional Parameters User Functional Parameters Electronic Label Programmer Guide User Application High-Level Commands Reading Absolute Position Reading the Absolute Position While Stationary Tracking the Absolute Position While Moving Setting a New Position Setting a User-Defined Position Resetting to Factory Default Service Opening Communication Closing Communication AqBiSS-to-RS-232 Converter High-Level Commands Hardware Setup Hardware Requirements Implemented Commands Internal Commands 46 Netzer Precision Motion Sensors Page 3 of 68

4 13. BiSS Master High-Level Commands Hardware Setup Read the Register Write to the Register Read the Encoder Internal Constants Internal Commands Translate Resolution Change to Coarse Mode Change to Fine Mode Read Current Position Read Parameters BiSS Low-Level Master Commands BiSS Initialization Read from Encoder Registers Write to Encoder Register Read Current Position Implementation Using C-8051F Hardware Signal Mapping Global Variables Hardware Setup Electrical Connections Implemented Commands Internal Commands Implementation Using IC-Haus Chip MB Electrical Connections Hardware Setup 53 Appendix A Register Mode Communication 54 Read Access to Registers 54 Write Access to Registers 56 Appendix B Sensor Mode Communication 58 Readout Sequences and Synchronization 58 Encoder Output Data Format 59 Appendix C CRC Calculations 61 Reading and Writing in Register Mode 61 Reading Data in Sensor Mode 62 EEPROM Registers 63 Netzer Precision Motion Sensors Page 4 of 68

5 Appendix D Electrical Schematics 67 Netzer Precision Motion Sensors Page 5 of 68

6 Introduction AqBiSS is a universal position encoder interface. Netzer Electric Encoders use the AqBiSS interface both for absolute and incremental, rotary and linear encoders. The AqBiSS combines the de-facto industry standard three channel incremental encoder digital quadrature (A quad B and Index) with the high speed and compact BiSS Bidirectional Serial Sensor standard interface. Netzer Electric Encoders use the AqBiSS interface both for absolute and incremental, rotary and linear encoders. This user guide is a comprehensive reference to the AqBiSS interface. It provides thorough information about The AqBiSS electrical interface How to read incremental and absolute position data How to implement a BiSS master hardware How to implement a AqB hardware counter Library of BiSS related software functions Available support tools and evaluation kit The AqBiSS to RS232 converter The document explains how the AqBiSS incremental and absolute encoders work and how you can implement them into your system. It assumes you have some understanding of CmotionCTT Incremental encoders can use AqBI only BiSS only Absolute encoders can use BiSS only AqBiSS (AqB and BiSS) In This Document Chapter 1 (this chapter) contains a list of references and explains some of the terminology used in this document. HTUChapter 2UTH introduces the AqBI and BiSS (AqBiSS) interface. HTUChapter 3UTH explains the absolute encoders mode of operation. HTUChapter 4UTH explains the incremental encoders mode of operation. HTUChapter 5UTH describes the wiring of the electric encoders, lists the contents of the evaluation kit, and explains how to verify PC-to-encoder communication. HTUChapter 6UTH provides a detailed description of the AqBiSS interface. HTUChapter 7UTH BiSS frame format & timing describes the BiSS timing requirements and each bit in the messages exchanged between the encoder and the BiSS master device. Netzer Precision Motion Sensors Page 6 of 68

7 Chapter 8 describes each AqBiSS register in detail. Chapter 9 introduces the central programming concepts used in the rest of the document. Chapter 10 provides an example of a user application. Chapter 11 introduces the high level commands implemented by all the methods described in this document. Chapter 12 explains how to use the AqBiSS encoder with a controller that has an RS-232 communication channel. Chapter 13 details the code needed for reading the absolute position based on the BiSS master high-level commands. The code demonstrates the requirements for calculating the absolute position. Chapter 14 lists the low level commands for interfacing to any BiSS master device and explains how to implement the procedures using the C-8051F320 controller, the IC-Haus chips. You can modify the code for different I/O devices as required. Appendix A explains register mode communication. Appendix B describes the sensor mode communication. Appendix C describes the CRC algorithms. Appendix D contains electrical schemata for alternative methods of interfacing with a BiSS master. Up-to-date and complete code ready for compilation is available from the Netzer web site: Terminology Acronym AZP BiSS CRC Fres I/O MA, SL MN UZP Explanation Absolute Zero Position The signed integer (24 bits) contains mapped zero position in counts for absolute encoders. After deducting the AZP, the zero is at a factory-defined zero. The factory-defined zero position is the same for all Netzer AqBiSS encoders. To ensure compatibility, you may not change this value. Bi-directional Serial Sensor interface. This protocol allows serial connections for up to seven sensors, for distances up to 100 meters using RS-422 differential signaling. Cyclic Redundancy Check Fine resolution, i.e. number of counts in one fine electrical cycle Input and output lines. BiSS communication lines. Algorithm used to determine an absolute location based on M coarse cycles and N fine cycles. See AN102. User Zero Position Signed integer (24-bits) containing the user-defined shift of the mechanical zero from the factory-defined zero. Netzer Precision Motion Sensors Page 7 of 68

8 References This user guide refers to the following documents: AN102 AqBiSS Electric Encoder - Calculating Absolute Position Application Note AN103 Absolute Position Feedback with ACS-Tech80 SPiiPlus Controller Application Note UG201 AqBiSS Electric Encoder Evaluation Kits User Manual BiSS application notes from the developers of BiSS, IC-Haus: HTUwww.biss-interface.comUTH Information about Altera, producer of the Cyclon EP-20xx chips: HTUwww.altera.comUTH Up-to-date manuals and code samples are available from the Netzer web site: HTUwww.netzerprecision.comUTH. Netzer Precision Motion Sensors Page 8 of 68

9 AqBiSS AqBI and BiSS Universal Interface for Electric Encoders AqBiSS is a new, fully digital interface for absolute and incremental encoders. It combines an A quad B incremental interface with the open-standard, high-speed Bidirectional Serial Sensor (BiSS) absolute interface. AqBiSS is a fast and robust interface suitable for real time communication. This document provides a detailed description of the AqBiSS interface and how to use it with NetzerAqBiSS Electric Encoders. A B i AqB,I Incremental Position MA SL BiSS Absolute Position Incremental Position Figure 1 AqBiSS signals Source for drawings: STA - Netzer Precision Motion Sensors Page 9 of 68

10 Figure 2 is a block diagram of a Netzer AqBiSS Electric Encoder (NE 2 ). AqBiSS Figure 2 Netzer AqBiSS electric encoder block diagram The NetzerAqBiSS Electric Encoder contains a fixed transmitter and receiver and a revolving rotor that is made of dielectric material, and is attached to the motor shaft. The transmitter contains two excitation plates (Tx) Fine and Coarse. The receiver consists of a receiving plate (Rx). The amplifier (A1) amplifies the received signal that its phase is a function of the rotor angle. The detector (A2) splits this signal. The split signals feed two low-pass filters (A3 & A4) resulting in a quadrant pair of sine and cosine of the rotor angle. The sine-cosine pair feeds the Sine-to-Digital (S/D) converter (A5). The S/D converts the sine-cosine pair into digital position data. The digital data is available to the user in two formats: AqB and Index format, and a digital word format that is accessed via the BiSS channel. The Serial EEPROM (A8) stores encoder parameters, which you can access through the BiSS channel. The microcontroller (A9) has two functions: 1. It generates a pair of high frequency (~55 khz) excitation signals that are shifted by 90º one relative to the other. 2. It controls, via the demultiplexer (A10), which set is excited the Fine or Coarse set. When the Coarse set is excited, the received data provides low resolution, absolute position information. When the Fine set is excited, the received data provides high resolution, incremental position information. By combining these two pieces of data, high resolution, absolute position is obtained. Netzer Precision Motion Sensors Page 10 of 68

11 Using AqBiSS with Absolute Netzer AqBiSS Electric Encoders Reading the Absolute Position The absolute position is read once, at the start of motion. After that the position is tracked by reading incremental changes. There are two ways to do this: 1. Use the BiSS channel for both the initial reading and for the incremental readings. For this configuration, the controller s BiSS interface must be high-speed, for example, a dedicated BiSS master chip. This configuration uses only four communication wires and is very robust. 2. Use the BiSS channel for the initial reading and then use the AqB for the incremental readings. In this configuration, a slow BiSS interface is adequate, for example, the Netzer s AqBiSS-to-RS-232 Converter. Upon initialization, the controller reads the position of the course channel and fine channel (via the BiSS) and calculates the absolute position. Afterwards, every sampling interval, the controller reads only the fine channel and updates the actual position. Finding the Initial Absolute Position In Netzer Precision Electric Encoders, more than one pole is used, meaning there is more than one electrical cycle per revolution. Both the mechanical angle and the electrical angle are measured. Figure 3 is an example of the two angle measurement structures. The inside structure is referred to as the coarse structure (in this example it has 3 poles). The outside structure is referred to as the fine structure (in this example it has 8 poles). Different mechanical (real) angles and their relative electrical angles are shown. The initial BiSS reading finds the absolute position using the MN algorithm, based on the coarse and fine readings. Netzer Precision Motion Sensors Page 11 of 68

12 angle angle angle Figure 3 Coarse and fine electrical angles and mechanical angle Using Only the BiSS for Position Reading Initializing Absolute Position Upon start-up/initialization (T n =0), the controller does the following: 1. Reads the registers. 2. Switches the encoder to coarse mode by setting the corresponding sin-to-digital converter (A5 in Figure 2) registers. 3. Reads the course channel value. 4. Switches the encoder to fine mode by setting the corresponding sin-to-digital converter (A5 in Figure 2) registers. 5. Reads the fine channel value. 6. Adjusts the CAA. 7. Calculates current absolute position (AZP) and assigns it to AP0 based on the MN algorithm. 8. Adjusts the user s zero position (UZP). Updating Actual Position Incrementally Afterwards, for each sampling interval (n>0): 1. Read fine channel. 2. Calculate the actual position using the following algorithm: Netzer Precision Motion Sensors Page 12 of 68

13 = B APBnB=APB(n-1)B + (FCPBnB-FCPB(n-1) B)B where APBnB Actual Position at sampling interval n. FCPBnB Fine Channel Position reading at interval n. The full algorithm is presented in HTUAN102UTH and the C code is in Section 0. Initial Reading Speed Limitations During initial reading of the course and fine channels, the motor should not move more then one half of the fine cycle, which imposes a maximum speed on the encoder as follows: Rotary encoders 60 rpm Linear encoders See the product data sheet Incremental Tracking Speed Limitations Between two tracking readings, the motor should not move more then one half of the fine cycle, which imposes a maximum speed on the encoder as follows: S < MST * N * 2 * Where MST Maximum Sampling Time msec N- number of fine poles S Speed in RPM Using BiSS Together with AqB for Position Reading Initializing Absolute Position Upon start-up/initialization (TBnB=0), the controller does the following: 1. Switch the encoder to coarse mode by setting the corresponding sin-to-digital converter (A5 in Figure 2) registers. 2. Read the course channel value. 3. Switch the encoder to fine mode by setting the corresponding sin-to-digital converter (A5 in Figure 2) registers. 4. Simultaneously read the fine channel and latch the controller s AqB counter value (CḆ 1B). 5. Calculate current absolute position and assign to AP0 based on MN algorithm. 6. Set CB0B APB0B (CB0B - CḆ 1B). This corrects the counter movement during step 5 from CḆ 1 Bto CB0B. The full algorithm is presented in HTUAN102UTH and an example of the implementation using Spii is in HTUAN103UTH. Actual Position Incrementally Afterwards, the counter automatically follows the position. Netzer Precision Motion Sensors Page 13 of 68

14 Speed Limitations Initial Reading Speed Limitations During initial reading of the course and fine channels, the motor should not move more then one half of the fine cycle, which imposes a maximum speed on the encoder as follows: Rotary encoders 60 rpm Linear encoders (see table in product data sheet) Incremental Tracking Speed Limitations Depends on the controller. Netzer Precision Motion Sensors Page 14 of 68

15 Using AqBiSS with Incremental Netzer AqBiSS Electric Encoders Using BiSS Alone for Position Reading Initialization Upon start-up/initialization (T n =0), the controller does the following: 1. Read the fine channel value and assign it to FCP0 & AP0. Updating the Actual Position Incrementally Afterwards, for each sampling interval (n>0): 1. Read fine channel. 2. Calculate the actual position using the following algorithm: AP n =AP (n-1) + (FCP n -FCP (n-1) ) where AP n Actual Position at sampling interval n. FCP n Fine Channel Position reading at interval n. The full algorithm is in AN102. The code implementation is in Section 0. Incremental tracking speed has the following limitation: between two tracking readings, the motor should not move more than one half of the fine cycle, which imposes a maximum speed on the encoder as follows: S < MST * N * 2 * where MST Maximum Sampling Time msec N- number of fine poles S Speed in RPM Using AqBI for Position Reading Read the controller s AqBI counter. There is no need to interface the BiSS channel. Netzer Precision Motion Sensors Page 15 of 68

16 How to Work with Netzer AqBiSS Electric Encoders Incremental AqBiSS Electric Encoders Using AqBI Alone Can be used with any motion controller that supports this de facto industry-standard interface. Cabling: Uses a total of 4 pairs (8 wires) as shown in green in Table 1. A+, A- B+, B- I+, I- 5V, GND Table 1 AqBI interface for incremental AqBiSS electric encoder Pin No Signals Description 1 Vc 5V Power Supply 2 GND Ground (return Power Supply) 3 A+ A positive (AqB), output 4 A- A negative (AqB), output 5 B+ B positive (AqB), output 6 B- B negative (AqB), output 7 I+ Index positive (AqB), output 8 I- Index negative (AqB), output 9 MA+ Master positive (BiSS clock), input 10 MA- Master negative (BiSS clock), input 11 SL+ Slave positive (BiSS data), output 12 SL- Slave negative (BiSS data), output Using BiSS Alone Motion controller must have native BiSS support or an external high-speed adapter. Cabling: Uses a total of 3 pairs (6 lines) as shown in green in Table 2. MA+, MA- SL+, SL- 5V, GND Netzer Precision Motion Sensors Page 16 of 68

17 Table 2 BiSS-only interface for AqBiSS electric encoder Pin No Signals Description 1 Vc 5V Power Supply 2 GND Ground (return Power Supply) 3 A+ A positive (AqB), output 4 A- A negative (AqB), output 5 B+ B positive (AqB), output 6 B- B negative (AqB), output 7 I+ Index positive (AqB), output 8 I- Index negative (AqB), output 9 MA+ Master positive (BiSS clock), input 10 MA- Master negative (BiSS clock), input 11 SL+ Slave positive (BiSS data), output 12 SL- Slave negative (BiSS data), output Absolute Electric Encoders Using BiSS Alone The requirements are the same as for the Incremental Electric Encoder working with BiSS alone (Section 0). Controller operation is as follows: 1. Upon power up, sample the Coarse channel position. 2. Switch to the Fine channel. 3. Sample the Fine channel position. 4. Calculate the absolute position (MN algorithm). 5. Continue sampling the Fine channel. Using AqB + BiSS The operation is the same as for BiSS alone (Section 0) except that after the absolute position is calculated, sampling continues via the AqB channel rather than via the BiSS channel. This configuration enables position based triggering. Cabling: Uses a total of 5 pairs (10 lines) as shown in green in Table 3. BiSS (MA+/-, SL+/-) AqB (A+/-, B+/-) 5V, GND Netzer Precision Motion Sensors Page 17 of 68

18 Table 3 AqB + BiSS interface for absolute AqBiSS electric encoder Pin No Signals Description 1 Vc 5V Power Supply 2 GND Ground (return Power Supply) 3 A+ A positive (AqB), output 4 A- A negative (AqB), output 5 B+ B positive (AqB), output 6 B- B negative (AqB), output 7 I+ Index positive (AqB), output 8 I- Index negative (AqB), output 9 MA+ Master positive (BiSS clock), input 10 MA- Master negative (BiSS clock), input 11 SL+ Slave positive (BiSS data), output 12 SL- Slave negative (BiSS data), output Interface to Controller (Closed Loop) To gain access of the absolute position, BiSS channel interface is required: Controllers with Built-In BiSS Support Controllers with native BiSS support can use either the BiSS channel or the AqB channel for sampling after absolute position calculation. An advantage of using the AqB channel is that it enables position triggering (if necessary). Controllers with RS-232 Channel If the controller does not have a BiSS channel but does have an RS-232 channel, then an external BiSS adapter can be used, such as the Netzer AqBiSS-to-RS-232 converter (shown in Figure 4). The AqBiSS-to-RS-232 converter provides a BiSS interface with AqBI pass-through. As there is a need to synchronize the controller counter with the data read from the BiSS channel, a latch signal (see Section 0) is sent from the Aqbiss_to_RS232_Converter to the controller. Netzer AqBiSS-to- RS-232 Converter Netzer AqBiSS Electric Encoder J2 J3 RS-232 Controller J1 AqBI Figure 4 Absolute encoder AqB + BiSS connection Netzer Precision Motion Sensors Page 18 of 68

19 Need to write a program in the controller that reads the coarse and fine position data, calculates the initial absolute position, and initializes the controller s software position counter. Afterwards it uses the AqB input to track the position. Using it this way enables position triggering based on the controller s hardware position counter Converter Power Requirements The AqBiSS-to-RS-232 Converter requires up to 500 mamp to operate with a fullyterminated Netzer AqBiSS Electric Encoder. If the controller cannot provide this power, then it is recommended to use the external power supply provided with the Aqbiss_to_RS232_Converter. The full implementation is described in AN103. Evaluation Kit (Open Loop) Netzer provides an AqBiSS Electric Encoder Evaluation Kit for open-loop operation via a personal computer. The kit includes all required hardware, including encoder and cables (Figure 5). The kit software provides an easy-to-use graphical interface (Figure 6), with no need for programming. The evaluation kit cannot be used for real-time control. Netzer AqBiSS Electric Encoder Netzer AqBiSS-to- RS-232 Converter J4 J2 J3 Power Supply PC Figure 5 Evaluation kit connection Netzer Precision Motion Sensors Page 19 of 68

20 Software Interface Figure 6 Encoder evaluation software Netzer Precision Motion Sensors Page 20 of 68

21 Contents Power cable CD-ROM RS-232 cable connection (underneath CD-ROM) Linear encoder AqBiSS converter Figure 7 Netzer AqBiSS Electric Encoder Evaluation Kit The Netzer AqBiSS Electric Encoder Evaluation Kit (Figure 7) includes the following: AqBiSS Electric Encoder mounted on a jig with connection cable AqBiSS-to-RS-232 converter (Section 0) Converter-to-RS-232 cable External power supply CD with Software and User's Guide For complete installation instructions, see HTUG201UTH. Verifying Communication Once you have connected the contents of the kit, you can check the communication between the encoder and the PC as follows: 1. From the Start menu, click Programs Accessories Communications * HyperTerminalHP TU UTHP. A HyperTerminal window opens. 2. On the File menu, click New Connection. A Connection Description dialog opens. 3. In the dialog, type the name of the connection, for example, NEE_COM2 if the AqBiSS converter is connected to COM2. Click OK. A Connect To dialog opens. Netzer Precision Motion Sensors Page 21 of 68

22 4. In the last field, select the relevant COM port and click OK. A COMx Properties dialog opens. Select for Bits per second, and None for Flow control. The parameters in this dialog should be exactly as shown in Figure 8. Click OK. A HyperTerminal screen opens. Figure 8 COM Properties dialog 5. Disconnect and reconnect the power to the converter. You should see "Netzer Precision VER X.XX" displayed on the HyperTerminal screen. 6. Hold down the letter B on the keyboard while simultaneously rotating or sliding the attached encoder. You should see the changing readings on the screen. 7. When the test is complete, close the HyperTerminal screen. Netzer Precision Motion Sensors Page 22 of 68

23 Detailed Description of the AqBiSS Interface AqBiSS combines a fast incremental A quad B + I (referred to as AqBI) interface with a digital absolute BiSS interface. AqBI Channel The AqBI channel provides incremental A-quad-B and Index signals. Signals A and B are electrically 90 out of phase with each other. The term quadrature refers to this 90 phase relationship. B leads A when counting up. A & B Signals and Quadrature Up Down Counting The AqBI waveform, with the encoder moves in the positive direction as shown in Figure 9. Figure 9 AqBI waveform Since each full cycle contains four transitions, or edges, an encoder that generates 2000 cycles/rev, for example, provides 8,000 transitions per revolution. Each transition generates a count as well, indicating the direction of travel, which determines whether to count up or down. This is done by establishing whether the transition is going high or going low, and what the state of the other signal is, as shown in Figure 9. Index Signal The index is a separate output signal that produces a single pulse (or transition change) at a unique position. The index is used to identify one or more reference positions. Netzer Precision Motion Sensors Page 23 of 68

24 BiSS Channel The Bidirectional digital sensor interface (BiSS) safeguards communication between position encoders or measuring devices and industrial controls, such as a drive control, for example, and if necessary can transmit measurement values from up to 8 sensors simultaneously. BiSS is an open industry standard that is gaining in popularity due to its low cost, high performance, and fewer required signal lines. BiSS is currently licensed free of charge. For more information, see HTUhttp:// Advantages of BiSS Figure 10 Point-to-point BiSS application (source: STA - Process information is directly digitized in the encoder, resulting in: High interference immunity The controller does not require analog interference suppression filters Transmitting and receiving electronics are simplified: No analog drivers and receivers No bidirectional driver components on both sides for encoder parameterization Serial data transmission ensures: Compact 2 signals (4 lines) Fast and suitable for real time control 10Mbit/sec and up to 100 meter cable Highly reliable differential lines, line delay compensation, and CRC Less connectors Development is simplified: Netzer Precision Motion Sensors Page 24 of 68

25 Lower design costs Less board space requirement for electronics enabling more compact designs Minimal declarations are only required for register data for the paramaterization if an adaptive master needs to be supported. Otherwise, the instruction list is reduced to one write and one read instruction. After that, the BiSS protocol controls when and what datum has to be sent or received. The process is defined through time conditions, which are transmitted together with the clock. Operational parameters are available in the memory area of the slave. Furthermore, there are system parameters and in addition, should the occasion arise, OEM parameters that can be defined by the users. This also means that the encoder interface BiSS already meets the requirements for an electronic type label. In addition, the storage of temporary system data is conceivable in this area, e.g. the software-defined zero point of a rotary encoder. The data transmission is protected through a cyclic redundancy check (CRC). This means that each data packet is provided with a check sum, which is evaluated by the receiving device. BiSS Specification BiSS is an open standard developed by ic-haus GmbH. For more information about BiSS, see HTUhttp:// Netzer Precision Motion Sensors Page 25 of 68

26 BiSS Message Formats This chapter and the next one describe the communication protocols and timing of the BiSS component of the AqBiSS encoder interface used in Netzer Precision AqBiSS Electric Encoders. The AqBiSS interface implements both an A quad B interface and a BiSS interface. These chapters cover the addresses and functions of the encoder's BiSS-related registers. This information enables you to define the requirements for the BiSS master device's hardware and software. The BiSS channel of Netzer Precision AqBiSS Electric Encoders is hardware-compatible with the SSI interface and has two unidirectional lines (Figure 11). It enables two types of communication: Sensor Mode. Maximum communication speed up to 10 MHz Register Mode. Maximum communication speed up to 250 khz In a case of a communication fault, the encoder will always return to a defined state. Figure 11 Encoder to controller logical connection via BiSS Overview of Sensor Mode In sensor mode a cyclic fast readout of encoder data is available without requiring addressing. When communication is initialized, the controller detects and automatically compensates for line delays, thereby enabling high data rates. The controller then simply continues the clock signal required for the encoder to output the data (Figure 12). To ensure the absence of faults in the transmitted data, use of the hardware-based CRC check mechanism is recommended. Figure 12 Signals in sensor mode (* includes error check) For more details, see HTUReading Data in Sensor ModeUTH on page 62. Netzer Precision Motion Sensors Page 26 of 68

27 Overview of Register Mode In register mode the registers in the encoder can be written or read. For this purpose, BiSS provides a special addressing sequence (Figure 13) where 3 bits are used for the subscriber ID addressing (for Netzer Precision AqBiSS encoders the subscriber ID address is always zero) and 7 bits are used for register addressing. To increase the transmission reliability the data of the addressing sequence is protected by a 4-bit CRC. Figure 13 Signals in register mode address sequence The 7 bits for the register addressing enable access to 128 registers of 8 bits each in the encoder. For reading out data from a register, the master has only to follow the addressing sequence with the corresponding number of clocks for the length of that message type (Figure 14). Figure 14 Signals in register mode read access During write access to the registers, the master transmits the data to be registered as PWM-coded data (Figure 15). For more details see Appendix A. Figure 15 Signals in register mode write access Communication Modes The BiSS channel can be used to perform a very fast readout of data or to perform write and read transfers to subscriber registers. Switching between these two communication modes is performed through a time condition at the start of each communication cycle. If the first low level of the MA signal is longer than the (configurable) time T tos, the sensors will be set to register mode. If it is shorter than T tos, then it will be set to sensor mode. Netzer Precision Motion Sensors Page 27 of 68

28 Timing The BiSS channel timing parameters are shown in Figure 16 and Figure 17 with reference to Table 4. Figure 16 Timing diagram in sensor mode Figure 17 Timing diagram in register mode (Read & Write) Netzer Precision Motion Sensors Page 28 of 68

29 Table 4 Timing parameters Value Name Description Notes Min Max Unit Sensor Mode T MAS Permissible Clock Period 100 ns T MASh Clock Signal High Level Duration 25 T tos ns T MASl Clock Signal Low Level Duration 25 ns Register Mode T MAR Permissible Clock Period 4 µs T idle Permissible Clock Halt (idle) 0 Indefinite T MARh Clock Signal High Level Duration T tor µs Read out of register data 50 % TMAR T MARl Clock Signal Low Level Duration T tor µs T MA0h Logic 0 High Level Duration % T MAR T MA1h Logic 1 High Level Duration % T MAR Timeouts Ttos Sensor Mode Timeout 1) µs Ttor Register Mode Timeout 2) µs Notes: 1) T tos may be assigned the value: 1, 4, 16, or 128 µs by programming the CFGTOS parameter of the encoder as described below. 2) T tor may be assigned the value: 32 µs, 256 µs, or 1 ms by programming the CFGTOR parameter of the encoder as described below. 3) The CFGTOR and CFGTOS parameters are placed on the register at register address 0x06 and have the format shown in Table 5. Table 5 BiSS channel parameter format Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 0x06 CFGTOR(1:0) CFGTOS(1:0) Do not change these bits! Possible values for CFGTOR and CFTOS are shown in Table 6. Netzer Precision Motion Sensors Page 29 of 68

30 Table 6 BiSS channel timeout settings CGFTOR Register Mode Timeout CFGTOS Sensor Mode Timeout 0x00 1ms. Factory default setting 0x00 0x01 256µs 0x01 16µs 0x02 32µs 0x02 4µs 0x03 Not permitted 0x03 1µs 128µs. Factory default setting See Appendix A for an explanation of register mode communication, and Appendix B for sensor mode communication. Netzer Precision Motion Sensors Page 30 of 68

31 Address Mapping The Netzer Precision Motion Sensors AqBiSS encoder provides access, via BiSS, to the encoder address range 00H to 7FH (127 bytes). The common address mapping is shown in Figure 18 and given in Table 7 below. BiSS Address (Hex) 7F 50 4F Encoder System Encoder Signature Parameters 20 1F Reserved EEPROM Legend: - Partially accessible to user - Inaccessible to user Power On Encoder Setup 10 0F 00 Functional Registers RAM Figure 18 AqBiSS encoder addressing map Table 7 AqBiSS encoder addressing Address, Hex Description 00-0F Functional registers. You can change some register values for absolute position definition. 10-1F EEPROM-stored power-on encoder setup (fine mode). You cannot change this area. 20-4F Reserved for future applications. 50-5F Encoder specific predefined storage area 60-7F Encoder Signature. You cannot change data in this zone Netzer Precision Motion Sensors Page 31 of 68

32 Functional Registers BiSS Address (Hex) 0F 0C 0B 0A Phase, Reference, Gain Ratio Cosine Offset Sine Offset Gain & Gain Ratio Timeout configuration Legend: - User can write to this register - User can only read from this register Resolution Figure 19 AqBiSS encoder functional register map Encoder System Parameters Address, Hex Description 60 One byte contains functional parameters Encoder setup data for Fine Mode (four bytes) 65 Encoder resolution code in Fine Mode Encoder setup data for Coarse Mode (four bytes) 6A Encoder resolution code in Coarse Mode 6B-74 Ten bytes contain functional parameters Encoder electronic label (four bytes) 79-7E Encoder serial number (six bytes) 7F Contains hexadecimal code 01H AqBiSS encoder memory space format Netzer Precision Motion Sensors Page 32 of 68

33 Encoder Operation Mode Switch Commands Switching the encoder operation mode is automatically performed by a read operation from the following BiSS registers: Reading from address 65H automatically switches the encoder to UFineU mode Reading from address 6AH automatically switches the encoder to UCoarseU mode The read operation from these addresses must be performed as single register read operation, not multiple consecutive register reads. Encoder Setup Data The encoder has two sets of parameters, one for each operation mode (fine and coarse). For proper operation in both modes, the encoder setup data must be copied into the encoder functional registers. NOTE: The read command from addresses 65 and 6A also automatically performs the Encoder Mode Switch command (Table 8): reading from 65 switches to fine mode and reading from 6A switches to coarse mode. Table 8 Encoder setup addressing Reading Address, Hex Fine Mode Coarse Mode Writing Address, Hex Description Gain and gain ratio setting values Sine channel offset setting value A Cosine channel offset setting value B Phase, reference, and gain ratio setting values 65 6A 00 Resolution setting value Encoder Resolution Code Encoder resolution code values are stored at address 65H for fine mode and at address 6AH for coarse mode. This value must be written into the functional register at address 00H after writing the encoder setup data. The format of this byte is shown below. Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reserved Resolution Code Permissible values for the encoder resolution code are given in Table 9. Netzer Precision Motion Sensors Page 33 of 68

34 Table 9 Encoder resolution Value, Hex Resolution per EC in counts Number of bits, transmitted via BiSS in sensor mode Group (1) , binary , binary , binary , binary , binary , binary , decimal 19 2, , decimal , decimal , decimal , decimal , decimal 17 3 (1) The Fine Mode Resolution ratio to Coarse Mode Resolution must be an integer value (Fine Mode Resolution divided by Coarse Mode Resolution without remainder). Therefore, the fine and coarse values should both be from the same group in Table 9. Encoder Functional Parameters Encoder functional parameter mapping is given in Table 10. Table 10 Functional parameter mapping Address, Bits Hex Reserved FLBI (11:8) 6B N(7:0) 6C CAA(11:8) N(11:8) 6D 6E 6F M(7:0) FLBI(7:0) CAA(7:0) 70 FMPL(7:0) 71 FMPL(15:8) 72 AZP(7:0) 73 AZP(15:8) 74 AZP(23:16) Netzer Precision Motion Sensors Page 34 of 68

35 Rotary Encoder Functional Parameters The rotary encoder functional parameters description for absolute encoders is in Table 11 and for incremental encoders in Table 12. Table 11 Absolute rotary encoder functional parameters Symbol N M CAA FMPL AZP FLBI Description for Absolute Rotary Encoder N unsigned integer (12 bits) that contains the number of Electrical cycles (ECs) in Fine Mode M the unsigned integer (8 bits), contains the number of ECs in Coarse mode. Coarse Adjustment Angle the unsigned integer (12 bits) contains the coarse position correction value for the absolute position calculation in coarse counts Not used. Equal to zero Absolute Zero Position The signed integer (24 bits) contains mapped zero position in counts for absolute encoders. After deducting the AZP, the zero is at a factory-defined zero. The factory-defined zero position is the same for all Netzer AqBiSS encoders. To ensure compatibility, you may not change this value. Not used. Equal to zero Table 12 Incremental rotary encoder functional parameters Symbol N M CAA FMPL AZP FLBI Description for Incremental Rotary Encoder N unsigned integer (12 bits) that contains the number of ECs in Fine Mode Not used. Equal to zero Not used. Equal to zero Not used. Equal to zero Not used. Equal to zero Not used. Equal to zero Linear Encoder Functional Parameters The linear encoder functional parameters description for absolute encoders is in Table 13 and for incremental encoders in Table 14. Table 13 Absolute linear encoder functional parameters Symbol N M Description, Absolute Linear Encoder N unsigned integer (12 bits), contains number of Fine EC in virtual scale length. M the unsigned integer (8 bits), contains number of Coarse ECs in virtual scale length. Netzer Precision Motion Sensors Page 35 of 68

36 Symbol CAA FMPL AZP FLBI Description, Absolute Linear Encoder Coarse Adjustment Angle the unsigned integer (12 bits) contains the coarse position correction value for the absolute position calculation in coarse counts Fine Mode Pitch Length The unsigned integer (16 bits) contains the Fine Mode scale pitch in micrometers (for example, 4000 in 4 mm Fine Mode scale pitch). Absolute Zero Position The signed integer (24 bits) contains mapped zero position in counts for absolute encoders. After deductin the AZP, the zero is at a factory-defined zero. All encoders have the zero defined at the same point when leaving the factory, to ensure compatibility, you may not change this value. Fine Left Brake Index - Unsigned integer (12 bits). Contains the Fine EC index at the left side of the virtual scale, used to define the singularity point for absolute position calculations. Table 14 Incremental linear encoder functional parameters Symbol N M CAA FMPL AZP FLBI Description, Incremental Linear Encoder N unsigned integer (12 bits), contains number of Fine ECs in the read head travel length. Not used. Equal to zero Not used. Equal to zero Fine Mode Pitch Length The unsigned integer (16 bits) contains the Fine Mode scale pitch in micrometers (for example, 4000 in 4 mm Fine Mode scale pitch). Not used. Equal to zero Not used. Equal to zero User Functional Parameters The address space from 0x50 to 0x5F is reserved for application specific data, which is programmed by Netzer Precision Motion Sensors, per application. You have access only to one register: UZP, which is factory configured to zero. You may store define an application-specific zero offset for this parameter for use after implementing the MN algorithm. The combination of the factory-set AZP and user-set UZP ensures that even if an encoder is replaced, the new encoder will point to the same absolute zero. For further explanation, see AN102. For the C code implementation that sets the SetPosition() function, see the accompanying ZIP file. (You can download the source code from the Netzer website). For C code implementation that uses the stored UZP to find the position, see Chapter 0. Netzer Precision Motion Sensors Page 36 of 68

37 Table 15 Application-specific address space Address, Hex Bits * UZP(7:0) 51 * UZP(15:8) 52 * UZP(23:16) 53 Reserved 54 Reserved 55 Reserved 56 Reserved 57 Reserved 58 Reserved 59 Reserved 5A 5B 5C 5D 5E Reserved Reserved Reserved Reserved Reserved 5F Reserved * User Zero Position (UZP) = signed integer of 24-bits containing the user-defined shift of the mechanical zero from the factory-defined zero. After the MN algorithm, the actual position is Abs = MN_pos - UZP AZP NOTE: For rotary encoders only: Abs = Abs mod (Fineres*finePoles) Where Abs = absolute position in fine counts MN_pos = position in fine counts calculated by the MN algorithm. UZP - User Zero Position (offset) AZP- Absolute Zero Position (offset) Netzer Precision Motion Sensors Page 37 of 68

38 Electronic Label The encoder electronic label has the following format: Address (HEX) High Byte Low Byte High Byte Low Byte Contents Encoder ID Encoder Sub-ID Bit 15 of the Encoder ID contains the encoder group code: 0 for rotary encoders 1 for linear encoders Bit 14 is reserved: 1 normal 0 optional Bits 13:0 contain the order number of the encoder kit inside the encoder group. Bit 15 of the Encoder sub-id contains the encoder subgroup code: 1 for incremental encoders 0 for absolute encoders Bit 14 contains the encoder interface type: 0 for AqBiSS 1 for BiSS only Bits 13:0 contain the modification code of the encoder. For full list of AqBiSS Encoder labels, contact HTUNetzer Precision Motion SensorsUTH. Netzer Precision Motion Sensors Page 38 of 68

39 Programmer Guide The BiSS channel of the AqBiSS encoder family enables digital access to the encoder position and registers. These registers configure the encoder operation mode and read the encoder position. The following chapters describe different methods of accessing AqBiSS encoder data using the BiSS Channel: PC / controller using an RS-232 to AqBiSS converter CPU / controller using a BiSS master Implementation of a BiSS master to encoder It is also possible to implement the BiSS master using a third-party Master chip such as that supplied by IC-Haus. Table 16 Benefits of each access method BiSS Access Method C-8051F320 controller IC-MB3 BiSS Master chip Advantages and Disadvantages Lowest cost. Cannot be used to close a control loop in real time through the BiSS channel. Fast enough to close a loop using only the BiSS channel. These methods permit: Reading the absolute position Setting a user-defined position Resetting to factory default settings Incrementally tracking the absolute position The attached ZIP file contains source code for the microcontroller. See the enclosed readme file. Netzer Precision Motion Sensors Page 39 of 68

40 Figure 20 describes all possible communication methods between the high level application and the AqBiSS encoder. The highlighted sections are implemented in the following chapters. Figure 20 Communication methods User Application Chapter 10 AqBiSS High-Level Commands Chapter 11 VHDL Master BiSS Master Low-Level Commands HChapter 14H IC-Haus BiSS Master Section 14.6 High Level Code Chapter 13 RS-232 AqBiSS Converter Low-Level Commands 8051F320 Controller Section 14.5 RS-232 AqBiSS Converter High-Level Commands Interface Code Chapter 12 AqBiSS Encoder Netzer Precision Motion Sensors Page 40 of 68

41 User Application This is an example of using the high level commands described in Chapter 0. It demonstrates use of the Generic Motion controller. The commands here allow: Reading the absolute position (long GetAbsolutePosition (void)) Setting user-defined position (void SetPosition (long SETP)) Reset to factory default values (void ResetToFactoryDefault(void)) The code, ready for compilation, is available at the HTUNetzer web siteuth. It runs the commands as shown in Figure 21. It uses the HTUActiveComport libraryuth to operate the serial port when using the Windows platform. Following are the user interface commands in DOS: Figure 21 Menu options Netzer Precision Motion Sensors Page 41 of 68

42 High-Level Commands This chapter details the three high level commands for accessing AqBiSS encoder data using the BiSS channel. These commands are used by all the methods described in later chapters. Figure 22 describes the connections. PC RS-232 (Example in Figure 21) or Controller RS-232 (Example in AN-103) AqBiSS Converter Figure 22 BiSS access Rotary or Linear AqBiSS Encoder Reading Absolute Position Reading the Absolute Position While Stationary long signed GetAbsolutePosition() The encoders are based on fine and coarse channels. To calculate the absolute position, the encoder 1) Reads (not synchronously) both the fine and the coarse channels at the one location. 2) Applies the MN algorithm. 3) Subtracts built-in mechanical offset values to find the absolute mechanical position of the encoder. The full algorithm is described in AN102. The command GetAbsolutePosition() returns the position in counts, relative to the factory location, or the user-defined location (if set). It returns the absolute position after performing the full MN algorithm. Notes Input Output This command may perform slowly, depending on the interface, and therefore should be used only upon startup. For faster performance, see Section 0. None. Absolute position in fine counts, relative to the user-defined position default. Netzer Precision Motion Sensors Page 42 of 68

43 Tracking the Absolute Position While Moving long TrackAbsolutePositionByFine(void) The TrackAbsolutePositionByFine() command reads only the fine value, compares it to the previously read fine value, and based on those readings, it determines the movement direction and extrapolates a new position. This operation is faster than the GetAbsolutePosition() command because it is based only on fine reading, which can be performed at the rate specified in the data sheet (up to 10Mbits/sec). The full algorithm is described in AN102. Notes Input Output Prior to using this command, set the initial position with the U command while the encoder is not moving. (The U command uploads the current absolute position as a reference to the TrackAbsolutePositionByFine() command.) None. Absolute position in fine counts, relative to the user-defined position default. Setting a New Position The Netzer encoders are factory-programmed such that the predefined zero position is set as specified in the data sheet, retrieved using the ResetToFactoryDefaults() command. Setting a User-Defined Position SetPosition(signed long pos) The SetPosition() command sets the encoder s current position as an absolute value. Notes Input Output The user-defined position is retained even after power down. User defined position within the required range. None. Resetting to Factory Default ResetToFactoryDefaults() To return to the factory default zero setting, execute the ResetToFactoryDefaults() command. Notes Input Output Resets the absolute position reading back to the factory setting, regardless of userinitiated changes. None. None. Service These commands open and close the communication channel. Netzer Precision Motion Sensors Page 43 of 68

44 Opening Communication int OpenCommChannel() The OpenCommChannel() command reads constants from the encoder memory. Notes The implementation is application-specific. Input User-defined. Output -1 if Open Failed error, 0 if OK. Closing Communication CloseComChannel() The CloseComChannel() command closes the communication channel. Notes The implementation is application-specific. Input None Output None Netzer Precision Motion Sensors Page 44 of 68