P300H P300 Series Modem Installation and Operating Handbook Page 202
SA-bus
The SA-bus message structure has a different format for messages from Master to Slaves, and from
Slaves to Master.
Master to Slave
The message format is:
idle
STX
(02H)
Address
(31H-61H)
Instruction
(30H-7FH)
`Body`
(1st char)
`Body`
(other chars)
`Body`
(last char)
ETX
(03H)
Checksum
STX:
The fixed character 02H
Address:
Slave Address, range 31H to 6FH (49-111
10
, ie 63 usable addresses).
Instruction:
Range 30H to 7FH. An ACK or NAK is automatically returned if the instruction
is
received (or there is no response if the message is not received !).
Body:
From zero to 128 characters (resulting in a maximum message length of 132
characters).
ETX:
The fixed character 03H
Checksum:
The Exclusive OR of the chars from the `STX` to `ETX` inclusive.
Slave to Master
The message format is:
idle
ACK / NAK
(06H/15H)
Address
(31H-61H)
Instruction
(30H-7FH)
`Body`
(1st char)
`Body`
(other chars)
`Body`
(last char)
ETX
(03H)
Checksum
ACK/NAK:
The fixed character 06H or 15H
Address:
As Master to Slave
Instruction:
Echo of the instruction to the Slave
Body:
NAK: One character, an echo of the instruction sent.
ACK: Where no response is expected (ie a `write` message), one character, an
echo of the instruction sent. Where a response is called for (ie a `query`
message resulting in a `read` response), the body is as defined for that
response.
ETX:
As Master to Slave
Checksum:
As Master to Slave
Message Categories
The remote M&C messages break down into the following categories:
1.
Messages to read the configuration & reconfigure the unit
2.
Messages to read the fault / operating status / performance of the equipment
3.
Messages to read the current test mode & change the test status
4.
Messages to request internally calculated values (eg data rates including overhead etc)
5.
Messages relating to the remote M&C status
6.
Messages relating to queries on the device itself, or option / cards fitted
7.
Messages relating to the capabilities of the devices, and remote upgrading.
8.
Message to perform an action (eg buffer centre)
9.
Messages to change Tx power / carrier in an abbreviated form
10. Messages to read the traffic log
11. Administrative messages
The following table summarises all messages, including the message categories listed above. A detailed
list of the content of each message is available on request from Paradise Datacom.
