Course on BASCOM AVR - (29) Theoretic/Practical course on BASCOM AVR Programming. Author: DAMINO Salvatore. SPI SERIAL EEPROM

Transcription

1 Course on BASCOM AVR - (29) Theoretic/Practical course on BASCOM AVR Programming. Author: DAMINO Salvatore. SPI SERIAL EEPROM In Embedded applications, among the most frequently used devices, there are the Serial EEPROM. These devices are available with different memory sizes, different packages and moreover with some, and different, Communication Protocols. In this chapter we ll descrive the SPI Protocol. SPI Serial EEPROM 25LC040 The EEPROM are memory, not Volatile: this means that they mantains the stored information even without power supply. The devices can be Written a very high number of times and they can be Read without limits, as standard RAM. 167

2 The management operations are defined by accurate rules, that are described below. The internal structure is reported in the following Diagram that lists all the logic blocks included in the device. Blocks Diagram of SPI Serial EEPROM 168

3 The communication is performed through 4 different signals: 1) The first (/CS) enables the EEPROM. 2) Tthe second (SCK) supplies Timings and Synchronizations. 3) The third (SI) sends data to device. 4) The fourth signal (SO) acquires data from the device. Send and Acquire operations can t be executed contemporaneously. Between the Data sent to EEPROM, there is the command that selects the operation to perform. Over the Read and Write commands naturally there is the address that specifies the location to use. The 25LC040 EEPROM supplies numerous possibilities for protection of saved data, both at Hardware level (pin /WE) or Software. It is important underline that one of these protections is automatically enabled after each write operation and it must be Always disabled by Firmware. In order to get a detailed and bright vision of the device, we suggest You firstly to read and study the specific component Data Sheet and then to try the developed examples. 169

4 Timing Diagram 170

5 Example.049. Byte R/W Management of a Serial EEPROM 25LC040 Added Definitions: Added Declarations: Added Instructions: Added Operators: Example program 49 of BASCOM AVR course. Test and management program for SPI EEPROM 25LC040, at byte low level, without BASCOM instructions. It performs the fundamental operations on the component by using a software SPI interface and by interacting with user on a serial console provided of monitor and keyboard with a fixed physical protocol at Baud, 8 Bit x chr, 1 Stop bit, No Parity. Electric Application Diagram of a SPI Serial EEPROM 25LC

6 This console can be another system capable to support a serial RS communication. In order to simplify the use it can be used a PC provided of one COMx line, that execute a terminal emulation program as HYPERTERMINAL or the homonym modality provided by BASCOM AVR (see IDE Configuration). The program works only when the GMM AM08 is mounted on Z2 socket of GMM TST3!! Experimental Card, on Prototype Board, of SPI Serial EEPROM 172

7 Example.050. R/W Management of a Serial EEPROM 25LC040 with Messages long up to 20 Characters, Displayed on Console Added Definitions: Added Declarations: Added Instructions: Added Operators: Example program 50 of BASCOM AVR course. Messages read and write on SPI EEPROM 25LC040. It performs the operations on the component by using a software SPI interface and by interacting with user on a serial console provided of monitor and keyboard with a fixed physical protocol at Baud, 8 Bit x chr, 1 Stop bit, No Parity. This console can be another system capable to support a serial RS communication. In order to simplify the use it can be used a PC provided of one COMx line, that execute a terminal emulation program as HYPERTERMINAL or the homonym modality provided by BASCOM AVR (see IDE Configuration). The program works only when the GMM AM08 is mounted on Z2 socket of GMM TST3!! 173