Up to three (3) RIO-RS232 modules may be attached to one RIO-PBA Profibus adapter.

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1 General Protocol Issues The RIO-RS232 module consumes 32 bytes of input and output data on Profibus. A fragmentation protocol is used for transferring serial data, requiring that a ladder program be written to either receive or transmit serial data. Up to three (3) RIO-RS232 modules may be attached to one RIO-PBA Profibus adapter. A parameter named Swap Header Bytes allows the user to change the order of the so called header bytes, which include the Fragmentation Byte, a pad byte, and two bytes containing the length of the serial data. As the actual number of serial data bytes is limited to 118 characters (102 in standard 8-byte module), only one byte contains length information. This length byte always appears two bytes after the Fragmentation Byte. In 2 nd and subsequent fragments, a pad byte is used, resulting in 30 bytes of data. Although this results in one fewer data byte being transferred, this will be offset by ease of programming (no shifting of data bytes in processor memory). This pad byte is not used by the 8-byte module. The user is also able to swap the serial bytes themselves, independently from the swapping of header bytes. The first byte of each message fragment (input and output) is called the Fragmentation Byte and has the following format: Reserved Command Fragment Count 0 Valid Command Field Values: Value Description 000 Idle 001 Receive (input data) 010 Send (output data) Reserved The Fragment Count begins with 1 for the first fragment transferred. A value of zero is not used while data is being transferred between the CPU and the module. The maximum Fragment Count value is 4, resulting in a maximum string size of 118 characters (28 chars in the first fragment and 30 chars for each of the three subsequent fragments). The second byte of some messages received from the module is a status byte and has the following bit definitions: Bit Description 0 TX Buffer Overflow Page 1 of 8

2 1 RX Buffer Overflow 2 RX Parity Error 3 Reserved set to 0 4 Reserved set to 0 5 Reserved set to 0 6 Fragmentation Error 7 New Input Data Available The module processes the data received from the PLC once each time it detects that the Fragmentation Byte s contents have changed. For this reason, the PLC program should change all other bytes before updating the Fragmentation Byte to avoid incorrect data from being processed by the module. The 3 rd and 4 th bytes of the first fragment of a transmit or receive operation are reserved for the length of the serial data. As the maximum length is 118, only one byte is required for this information. Whether the byte is the 3 rd or 4 th depends on the parameter Swap Header Bytes. If Swap Header Bytes is disabled, the length is found in the third byte. If Swap Header Bytes is disabled, the length is found in the fourth byte. Message Transmission Transmission only works in handshake mode. In other words, the 232 module will only transmit a serial message when an entire new message is received from the ladder program. However, no transaction ID is used. PLC program waits until 232 module reports IDLE status before initiating a transmit sequence. A pad byte is inserted between the fragmentation byte and the length field allowing the length bytes to fall on a word boundary. If the ladder program violates the fragmentation protocol (skipping a fragment for example) when attempting to transmit a string, an idle message with the fragmentation error bit set will be sent by the module. The module will not check the contents of the bytes containing serial data. If two consecutive fragments with the same fragment count and differing data bytes are received by the module, only the oldest data will be processed and applied. The number of bytes to be transmitted is contained in the first fragment in one of two bytes and the format of these bytes is determined by the use transmit length and swap header bytes configuration parameters. If the use transmit length parameter is disabled, the two length bytes still occur but are ignored by the module. If use transmit length is enabled, the module will expect to receive only enough fragments to transmit the expected number of bytes. For example, if the maximum size is defined as 20, but a message with a size of 6 is received, the module will expect to receive only 2 fragments from the PLC. Page 2 of 8

3 If use transmit length is enabled, and a size of 0 is specified, the module will expect the defined maximum number of bytes to be transferred. If use transmit length is disabled, the maximum number of fragments (based on max_transmit_chars specified) must be sent to the module. If too many fragments are received, the module will produce an idle message with the Fragmentation Error bit set. The data already received from the CPU, however, will have already been serially transmitted. If an end delimiter is defined as being contained in the string, that delimiter character must be contained in the string memory area written by the CPU. The behavior in this instance will mimic the DNet behavior. If use transmit length is disabled, the data will be transmitted when either the end delimiter char is detected or the max characters are received. If the end delimiter char appears earlier in the string than expected, the smaller string will be transmitted by the module. Transmit Example: Transmitting string abcdefghijklmnopqrstuvw having length 23 (0x17). This is a simple case requiring only one fragment. Strings requiring multiple fragments would follow the same pattern (frag bytes, etc.) of the 8 byte module. Ladder program waits until idle status is received from the module: Ladder program sends first fragment to be output: x21 00 x17 00 a b c d e f g h i j k l m n o p q r s t u v w send pad length data Module still reports idle state. Must wait until status indicates that it s receiving the fragments to be serially transmitted Ladder program continues to send first fragment to be output: x21 00 x17 00 a b c d e f g h i j k l m n o p q r s t u v w send pad length data Page 3 of 8

4 Module now reports idle state with the correct fragment count. x01 00 Ladder program sends idle message to module releasing the module: 00 idle unused The ladder program must wait again until the idle status is received from the module before initiating a subsequent send operation. x01 00 Page 4 of 8

5 Message Reception Reception only works in handshake mode. In other words, the 232 module will only transfer a received serial message when instructed to do so by the ladder program. However, no transaction ID is used. Module indicates to the PLC that it has a received serial message to transfer by asserting the New Input Data Available bit in the Status Byte. The PLC then respond s with a Receive command with a Fragment Count of 0. When Pad Mode is enabled, the number of fragments corresponding to the defined Max Receive Chars are transferred to the PLC. When Pad Mode is disabled, the number of fragments corresponding to the current number of bytes are transferred to the PLC. When Use Receive Length is defined to be enabled, the number of fragments corresponding to the current given size are transferred to the PLC. Certain configurations should probably be avoided by most users. For example, with Pad Mode disabled, Use Receive Length disabled, and End Delim Mode set to exclude, it would be very difficult to know which characters in the final fragment belong to the most current serial data, and which are from previous messages. Receive Example: This is a simple case requiring only one fragment. Strings requiring multiple fragments would follow the same pattern (frag bytes, etc.) of the 8 byte module. The ladder program detects an idle status with the New Input Data Available bit set. 00 x80 idle status Unused Ladder program sends fragment indicating that the module should transfer the received data to the CPU: x10 rcv unused The module sends the first fragment, with the New Input Data Available bit still set. x11 x80 x17 00 a b c d e f g h i j k l m n o p q r s t u v w rcv status length Data unused Page 5 of 8

6 The ladder program responds with an idle command field value indicating that the first (and last) fragment has been received: x01 idle unused The module sends the idle fragment. If another input message were available, the New Input Data Available bit would now be set: x00 00 Page 6 of 8

7 Appendix A Configuration Information RIO-RS232 Configuration Parameters on Profibus (Default Values in RED) Name Type Description General Parameters Serial Framing Bit Field 9 options (4 bits) -7N2,7E1,7O1,8N1,8N2,8E1,8O1, 7E2,7O2 Serial Baudrate Bit Field 6 options (3 bits) ,1200,2400,4800,19.2K,38.4K Swap Header Bytes Bit 2 options (1 bit) - enable, disable Receive (Input Data) Parameters Max Rcv Chars USINT (20) Rcv Start Delim Mode Bit Field 3 options (2 bits) - none, exclude, include Rcv Start Delim Char CHAR 1 char (7 or 8 bits long) (58) Rcv End Delim Mode Bit Field 3 options (2 bits) - none, exclude, include Rcv End Delim Char CHAR 1 char (7 or 8 bits long) (13) Use Receive Length Bit 2 options (1 bit) - enable, disable Pad Mode Bit 2 options (1 bit) - enable, disable Pad Char CHAR 1 char (7 or 8 bits long) (0) Rcv Swap Mode Bit Field 4 options (2 bits) - disabled, 2byte, 3byte, 4byte Transmit (Input Data) Parameters Max Xmt Chars USINT (20) Xmt End Delim Mode Bit Field 3 options (2 bits) - none, exclude, include Xmt End Delim Char CHAR 1 char (7 or 8 bits long) (13) Use Transmit Length Bit 2 options (1 bit) - enable, disable Xmt Swap Mode Bit Field 4 options (2 bits) - disabled, 2byte, 3byte, 4byte The above listed parameters can be placed in 9 bytes of configuration data 3 bytes of bit fields and 6 bytes of USINT/CHAR data. Page 7 of 8

8 Config Block - Indicates areas containing non-configuration data Product Code High Byte Product Code Low Byte Extended diagnostics Pad Mode Baud Rate Serial Framing Max Transmit Chars (1-118) reserved Swap Hdr Bytes Xmt End Delim Mode (0-2) Xmt Swap Mode (0-3) Xmt Delim Char ( ) Max Receive Chars (1-118) Rcv End Delim Mode Rcv Start Delim Mode Rcv Swap Mode Use Xmit Length Receive Start Delim Char Use Receive Length Receive End Delim Char Pad Char Default Config Block Values Offset Value 0 0x00 1 0x6E 2 0x89 3 0x x14 5 0x08 6 0x0D 7 0x14 8 0x x3A 10 0x0D 11 0x00 Page 8 of 8

VPGate Manual PROFIBUS to serial

VPGate Manual PROFIBUS to serial Important information Purpose of the Manual This user manual provides information how to work with the VPGate PROFIBUS to serial. Document Updates You can obtain constantly