Status request

Direction

MTP 3 -> MTP 2

Description

Requests a special function supported by the MTP 2 layer.

The following table lists the message parameters:

Type

Field

Description

U8

Message Type

0x78

S16

Service Provider ID

MTP 2 reference number for the link on the TX board. Valid values are 0 through 15.

S16

Action

Action to take. Possible values are:

0 = No action; indicate change in status to MTP 2 as specified in Status field

1 = Retrieve backward sequence number

2 = Retrieve unacknowledged messages

3 = Drop all queued transmit messages

U32

Status

Status change being indicated to MTP 2; relevant if action is 0 or 2.

When action = 0, possible values are:

0 = Local processor is down

1 = Local processor is up

2 = Emergency condition

3 = Emergency ceases

 

When action = 2, the only possible value is the starting sequence number, usually retrieved from an MTP3 COO or COA, which retrieves unacknowledged messages from the board.


Details

The MTP 2 layer supports the following special functions:

MTP 2 returns a status confirmation message containing the current BSN (last acknowledged sequence number) for a link to the application in response to a retrieve BSN status request. MTP 2 also returns a status confirmation message in response to a retrieve messages status request, but only if there are no unacknowledged messages to be retrieved. If there are unacknowledged messages to be retrieved, a data confirmation message indicating a status of unacknowledged [more | last] is sent to the application for each message. The last message indicates that it is the last. No status confirmation message is returned to the application.