Appendix: Serial Programming Interface; Introduction; Command And Response Formats - Arcam DV79 Handbook

Appendix: Serial programming interface

Introduction

This section of the document describes the remote control protocol for controlling the DV79 via the
RS232 interface.
Conventions
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Data transfer format
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Command and response formats

Communication between the RC and the DV79 takes the form of sequences of ASCII characters, with
all commands and responses having the same basic format. With the exception of status triggers (see
below), the DV79 shall transmit only to respond to communication from the RC. The DV79 shall always
respond to a received command.
Each transmission by the RC shall be five bytes long in the following format:
<STR> <CC> <P1> <P2> <ETR>
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Each response by the DV79 shall be seven bytes long in the following format:
<STR> <RC> <AC> <P1> <P2> <P3> <ETR>
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The RC shall transmit commands and receive answers according to the following procedure:
1. The RC shall transmit a command.
2. Having issued a command, the RC shall wait at least 100ms before transmitting a subsequent
3. The RC shall analyse the RC, AC and Px values of a received message to decide whether the
4. The time from the completion of command transmission by the RC to the beginning of the
5. The DV79 shall not accept any commands from the RC for five seconds after the power switch is
The exception to the above communication protocol is when 'status triggers' are enabled by the RC (using
the 'Status Triggers' command). In this case, the DV79 shall transmit messages whenever the status of
the player changes. These messages shall be transmitted by the DV79 at asynchronous intervals.
State changes as a result of other inputs
It is possible that the state of the DV79 may be changed as a result of user input via the front panel
buttons or via the IR remote control. Changes resulting from these inputs shall be relayed to the RC
(using the appropriate message type) only if 'status triggers' have been enabled by the RC.
For example, if the user changed the front panel display brightness using the
control, a display message (defined below) would be sent to the RC. A similar action would be taken for
all other state changes.
Answer codes
The following answer codes are defined:
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If the answer code returned is anything other than 'Command OK' or 'Status update' then all parameter
fields in the return message become 'reserved'.
The remote controller is referred to as the 'RC', with the DV79 called the 'DV79'.
All values in this section are hexadecimal values, unless otherwise specified.
Transfer rate: 19,200bps.
1 start bit, 8 data bits, 1 stop bit, no parity, no flow control.
STR (Start transmission): 0x21
CC (Command code): the code for the command
Px (Parameter code): the parameters for the command
ETR (End transmission): 0xD
STR (Start transmission): 0x21
RC (Reply code): = command code
AC (Answer code): answer code (see below)
Px (Parameter code): the parameters for the reponse
ETR (End transmission): 0xD
command (otherwise commands may be lost). Ideally, the RC shall wait for an answer from the
DV79 before issuing the next command.
command has been executed normally.
response by the DV79 shall be maximum two seconds.
turned on or a 'power-on' command is recieved.
Command OK '@' (0x40):
Command ACC 'A' (0x41):
Status update 'B' (0x42):
Invalid command '0' (0x30):
Invalid request '5' (0x35):
The command has been accepted and processed completely.
The command has been accepted but not yet processed fully.
Status change message
The command or command format was invalid
The command is not valid for the current player state
button on the remote
DISP
DV79
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