ARC130S SECTION
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ARC130S 060801 Version 1 Issue 1
4.32
PROTOCOL
The ARC130S software supports a second RS 422 remote control protocol. This has been done so that the
ARC can be controlled by Philips automation systems that are unable to support the full command set of the
Snell & Wilcox ARC’s.
If the alternate protocol is selected the RS 422 link is automatically switched to eight data bits, one stop bit and
no parity. The baud rate is selectable from the ARC menus and may be set to 38400, 9600 or 4800 baud. Note
that the RS 422 data bits menu item only controls the number of RS 422 data bits in use when the default Snell
& Wilcox protocol is in use.
The protocol accepts messages of the form: -
<stx><address><command><etx>
Where: -
<stx>
=
One byte with hexadecimal value 0x02. This indicates the start of a message packet.
<address> =
One byte representing the ARC address. The MSB is always set to one. This byte can take a
value in the range 0x81 to 0xE3 representing addresses one to ninety-nine (decimal). The
ARC checks that the value is in this range and will respond to any valid address. Commands
with an address outside the valid range are ignored.
<command>=
One byte which represents the desired command. The MSB is always one. See table below of
valid command numbers.
<etx> =
One byte with hexadecimal value 0x03. This indicates the end of a message packet.
The accepted commands are either a Poll command or a Recall preset command.
If a Poll command is received then the ARC will respond with an <
ACK>
byte (0x04) if the ARC is available to
receive messages. If a communications error occurs, a <
NAK>
byte (0x05) will be sent by the ARC.
If a Recall Preset command is received, the ARC will respond with an <
ACK>
byte (0x04) if the message is
received and the Preset is updated. If a communications error occurs, a <
NAK>
byte (0x05) will be sent by the
ARC and the Preset will not be updated.
Command Byte
Command Name
ARC Action
0x80
Poll
0x90
Recall Preset 1
Recall User Memory 1
0x91
Recall Preset 2
Recall User Memory 2
0x92
Recall Preset 3
Recall User Memory 3
0x93
Recall Preset 4
Recall User Memory 4
0x94
Recall Preset 5
Recall User Memory 5
0x95
Recall Preset 6
Recall User Memory 6
0x96
Recall Preset 7
Recall User Memory 7
0x97
Recall Preset 8
Recall User Memory 8
0x98
Recall Preset 9
Recall User Memory 9
0x99
Recall Preset 10
Recall User Memory 10
0x9A
Recall Preset 11
Recall User Memory 11
0x9B
Recall Preset 12
Recall User Memory 12
0x9C
Recall Preset 13
Recall Auto Mode
Table - RS 422 Command Numbers
