Serial interface limitations

In some sections of Clipsal Documentation they state that serial interface command buffer is limited to a maximum of 21 bytes (42 charcaters) and in other sections the manual says that the "SAL Data" part of the command stream is limited to (14 - 21 bytes) - depending on network bridges.

Can anyone clear up some confusions on this matter

1. Does the 21 byte maximum include the "\" and the "header byte" at the start and finally the "checksum" byte at the end of the command string?
For example "\05..............CS"

2. If the maximum number of bridges are used, then 8 bytes are required (for additional bridge addressing) so if they state that the SAL Data portion needs to be limited to 14 bytes then something doesn't seem right ?

3. Also does this 21 btye buffer limit place any restrictions on the length of data that the Serial Interface can recieve and relay on to third party devices -- for example is the serial interface reception resposes limited to 21 bytes also?

4. Also can anyone confirm that the CNI moudule behaves exactly the same as the PC Serial interface module (expect for access via telnet) - in other words does the CNI accept exactly the same commands and behave exactly as the Serial interface once a TCIP connection has been established?

many thanks
Coll

 

For any command sent to the Serial Interface, there cannot be more than 45 characters between the leading \ and the <cr>. So, in direct answer to your question, the 21 byte limit does not include the '\' or the 'checksum' but it does include the header byte.

If the maximum number of bridges are used, the total number of network routing information required is 8 bytes. If there is no network bridge routing, then the network routing information consumes 1 byte. The difference is 7 bytes.

21 bytes is the limit.

PCI and CNI behave in exactly the same way with exactly the same constraints.

 

Hi syn

I have played around a little with a PCI and have found that the 21 btye limit if different and depends on if its a transmission or reception string?

Usually the PCI will hold more bytes for reception than transmission but I don't really know why this is so?

If this helps?

Peter