[Reference]
Transmission Sequence
Transmission Protocol
RS232C
Host |
|
| |
(1) | ENQ (05h) |
|
|
(2) | EOT (04h) | STATUS | ALM CODE |
(3) | Data Block | Received | x6 |
| |||
(4) | ACK (06h) | Data |
|
|
| ||
(or NAK (15h)) |
| x5 | |
|
| ||
(5) | ENQ (05h) |
| x4 |
(6) | EOT (04h) |
| x3 |
|
|
| |
(7) | Data Block | Transmitted | x1 |
(8) | ACK (06h) | Data |
|
|
| ||
(or NAK (15h))
Line Control
Direction of transmission and conflict are solved.
Reception mode …The module enters reception mode after receiving ENQ and returning EOT. Transmission mode … The module enters transmission mode after sending ENQ and receiving EOT. When there occurs a conflict between the transmitting module and receiving module:
When subsequent to transmission of ENQ, a slave receives ENQ while waiting for EOT, priority is given to ENQ sent from a maser, and the slave enters the reception mode.
Transmission Control
Entering transmission mode, a module transmits a command block continuously and then waits for reception of ACK. When the module receives ACK, transmission is complete. When the number of transferred command bytes is incorrect, ACK may not be returned. When ACK is not returned within T2 period, or when NAK or any code other than ACK is received, transmission retry will be executed. The retry will start with ENQ.
Receiving Control
Entering receiving mode, the module receives transmitted blocks continuously. It obtains the number of command bytes from the first byte, and receives as many command bytes as that number plus 3. When the sum of received data is zero, reception is considered successfully ended and ACK is returned. When abnormal checksum or timeout between characters occurs, NAK is sent.
Reference
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