Amtelco infinity series - Commands and Responses Protocol; Sending Commands to the Board

Communicating with the Host• 5-2 •
The H.110 Basic Rate ISDN Board
In addition to the two main mailboxes, there are two auxiliary mailboxes
that are used for passing Layer 3 messages to and from the board. These
mailboxes are only used in conjunction with the “LC” and “LR” command
and response messages in the main mailboxes. Each of these auxiliary
mailboxes begins with two bytes indicating the length of the Layer 3
message (low order byte first) and 260 bytes for the body of the message
(the maximum size of a information field for Q.931 messages). The
mailbox for messages to the board has an offset of 1400h and the mailbox
for messages from the board is at an offset of 1600h.
To send a Layer 3 message, the transmit flag for the main mailbox must be
clear. The message and its length is first placed in the auxiliary mailbox.
An “LC” or “LR” command is then placed in the main mailbox, and finally,
the transmit flag is set to 01h. It is important that both the Layer 3 message
and the command be placed in the appropriate mailboxes before the
transmit flag is set.
The presence of a Layer 3 message from the board is indicated by either
an “LC” or “LR” message in the main mailbox. The Layer 3 message must
be read before the receive flag is cleared. Failure to do so may result in the
message being overwritten.
5.1 Commands and Responses Protocol
This section describes the necessary step-by-step procedures for the host
to send a command to the board and to remove a response from the board.
5.1.1 Sending Commands to the Board
The basic steps to sending a command to the H.110 BRI ISDN Board are:
1. Build a command. Broadly speaking, a command is a string of
ASCII characters with a NUL (00h) termination character.