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RS-232C Interface
3. Protocol
■ Receiving format (personal computer → VTR)
General format: stx command [:data] [;command [:data]] etx
stx:
02h (HEX)
; (semicolon):
3Bh command delimiter
command:
ccc
ccc: command (3 ASCII characters)
: (colon):
3Ah parameter delimiter
data:
parameter (any number: based on command)
etx:
03H
In some cases, the format does not contain what is enclosed in the square brackets.
■ Example
stxO S Petx (stop command)
02,4F,53,50,03 (stop command in HEX notation)
■ Sending format (personal computer ← VTR)
•
Command receive verification
ack (with error-free receipt of command)
nak e (when communication error has occurred)
e: error code
1: parity error
3: framing error
4: overrun error
•
Response message
General format: stx message [:data] etx
•
Error message (when error has occurred in protocol or command)
General format: stx error message etx
ack:
06h
nak:
15h
stx:
02h
message:
mmmm
mmmm: message (any number of ASCII characters)
: (colon):
3Ah parameter delimiter
data:
parameter (any number)
error message:
ERnnn (error code)
nnn: 3-digit number
001: Invalid command (not supported)
002: Invalid parameter
003: Receive buffer overflow
004: Defective connection
etx:
03h
■ Explanatory description
•
As soon as the receive buffer becomes full, receive buffer overflow is returned, and subsequent commands are
canceled.
•
The ACK or NAK response must commence within 20ms.
•
When a new command has been received during the processing of an non-interruptible command, the receive
verification code is returned within 20ms, after which the applicable ERROR code is returned, and the
processing of the previous command is resumed.
•
When it takes time for execution to be completed, it is to be possible for the next command to be processed (in
principle, after the ACK response) without waiting for the completion of the said execution. (This applies only to
commands whose processing can be interrupted.)
•
When a command which does not entail a transfer of the deck mode is received, the message of having
completed the received command is returned regardless of the deck mode.
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