AVL通讯协议.doc

Serial communication protocol Master/Slave 1.1 ASCII - Protocol Each measurement value starts with a code number ( 3 characters ). You can look in the code table on the end of this document to know the value-name. The characters between the code and ETB or HT are the value with some blanks on the end. If a value is not ok we don’t send it to the PC, therefore the length of the protocol is not always constant. 1.2 Master mode The measurement tool send a data block to the PC. The PC have to wait for this block and send after controlling the checksum a answer ( ACK + ETB ) to our tool. ACK ... checksum is OK NAK ... checksum is NOT OK, we can repeat the datablock 2 times. Parameter: 9600 baud, 8 data bit, 1 stop bit, NO parity 2 sec timeout for RS232 Datablock - Format: AVL465 / AVL4000 -- PC STX start of data block nnn vvvv _ _ HT 1. value nnn vvvv _ _ HT 2. value . . . nnn vvvv _ _ HT last value ‘5 ‘ ‘A ‘ 2 byte checksum ASCII 0..F ETB “ end of data block nnn = ( code table vvvv = value with some Blanks on the end PC -- AVL465 / AVL4000 PC test the checksum and send the answer ACK checksum was OK ETB or NAK checksum was not OK ETB 1.3 Slave mode ( ISOTEC - MODE) The PC send a question (ENQ) to the measurement tool. If our tool is not ready to send a data block, we answer with a NAK. If our tool is ready, we send the data block. The PC have to wait for this block and send after controlling the checksum a answer ( ACK or NAK). ACK : the checksum of the data block was OK, if there are more than one data blocks we send the next one. NAK : the checksum of the data block was not OK, we can repeat the data block 2 times. Parameter: 9600 baud, 8 data bit, 1 stop bit, NO parity 2 sec timeout for RS232 Format: Slave mode STX start of data block nnn vvvv _ _ ETB 1. value nnn vvvv _ _ ETB 2. value . . . nnn vvvv _ _ ETX last value ‘5 ‘ ‘A ‘ 2 byte checksum