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Communications
State Transition Diagram
RS232C Communications
There are requests
for transmission
(within the number
of retries).
ENQ transmission
and T2 start.
There are requests for
transmission but the number of
retries is exceeded.
The number of retries is to be
reset once. A request for
transmission is cleared.
T2 timeout
ENQ
NAK is transmitted.
T2 stop
EOT is
transmitted.
T2 start
Waiting for the number
of command bytes
Transmitting Module
Waiting for EOT
ENQ is received and in slave
mode.
ENQ is returned to receiving
buffer
(To reception
processing)
T1 times out or checksum
error occurs when size
becomes 0.
NAK is transmitted.
T1 stop
The number of command bytes is
received.
Size
Number of command bytes +3
Sum
Number of command bytes
T1 start, T2 stop
Receiving module
EOT is received.
Size
Number of command
bytes + 3
T2 stop
Transmission of block
T2 timeout
The number of retries
is counted once.
T2 stop
Transmission buffer is
cleared.
Waiting for ACK/NAK
NAK is received or T2
times out.
The number of retries is
counted once.
T2 STOP
Transmission buffer is
cleared.
Idling
Receiving
Remaining blocks
One character is received.
Size
Number of command bytes -1
Sum
Sum + received characters
T1 start
164
One character is received.
Size
Number of command
bytes - 1
Size becomes zero.
T2 START
ACK is received.
The number of retries
is reset.
T2 stop
The request for
transmission is cleared.
Reception is successful
(checksum is OK when size
becomes 0).
ACK is transmitted.
T1 stop
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