MP_START_AR (Start Autoresponse) and MP_STOP_AR (Stop Autoresponse) mpioctl MPQP Device Handler Operations

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AIX Version 4.3 Kernel and Subsystems Technical Reference, Volume 2

MP_START_AR (Start Autoresponse) and MP_STOP_AR (Stop Autoresponse) mpioctl MPQP Device Handler Operations

Purpose

Permits the Multiprotocol Quad Port (MPQP) to exit or enter Autoresponse mode.

Description

The MP_START_AR and MP_STOP_AR operations permit the MPQP to enter and exit Autoresponse mode. When the cmd parameter is set to the MP_STOP_AR operation, the device exits from Autoresponse mode. All received data is sent up to the host. The data link control (DLC) receives an end-of-autoresponse status in the status_block structure of the CIO_GET_STAT operation.

When the cmd parameter is set to the MP_START_AR operation, the port is put into Autoresponse mode. The DLC supplies the address and control bytes for receive compare and transmit in the t_auto_resp structure pointed to by the extptr parameter. This structure contains the following fields:

`rcv_timer`	Identifies the time in 100-msec units that the adapter waits after a frame has been transmitted before reporting an error.
`tx_rx_addr`	Contains the 1-byte address used for compare on the receive frames and as the address byte on transmitted frames.
`tx_cntl`	Specifies the control byte used for transmitted frames.
`rx_cntl`	Identifies the value of control byte on receive frames used for receive compare.

Autoresponse mode is applicable for Synchronous Data Link Control SDLC protocol only. Autoresponse reduces the amount of system overhead during nonproductive link communications. While Data Termination Endpoints (DTEs) are exchange-control information to maintain the link, the adapter can respond to polls from the host without generating any system interrupts.

When in Autoresponse mode, the MPQP adapter compares the receive address and control bytes with the values supplied by the DLC. If a match is found, it generates a response frame with the address and control bytes given in the MP_START_AR operation. When a response frame is transmitted, a timer is started with the value given in the rcv_timer field. If the adapter does not receive a frame before the timer expires, it detects an error and exits Autoresponse mode.

The following five conditions cause the MPQP adapter to exit Autoresponse mode:

A receive time out occurs.
A transmit time out occurs.
A poll/final frame is received that does not compare with the control data given in the autoresponse operation.
A fatal link error occurs. Fatal errors include data rate select (DSR) dropped and X.21 cleared received.
A stop autoresponse command is received from the DLC.

If one of these errors occurs, the adapter exits Autoresponse mode and stays in receive mode. Polls received after these errors occur are passed to the DLC.

Execution Environment

The autoresponse operations can be called from the process environment only.

Return Values

ENOMEM	Indicates no mbufs or mbuf clusters are available.
ENXIO	Indicates the adapter number is out of range.

Implementation Specifics

The autoresponse operations function with a 4-Port Multiprotocol Interface adapter been correctly configured for use on a qualified network. Consult the adapter specifications for more information on configuring the adapter and network qualifications.

Related Information

The CIO_GET_FASTWRT ioctl Communications PDH Operation.

The CIO_GET_STAT mpioctl MPQP Device Handler Operation, CIO_HALT mpioctl MPQP Device Handler Operation, CIO_QUERY mpioctl MPQP Device Handler Operation, CIO_START mpioctl MPQP Device Handler Operation, MP_CHG_PARMS mpioctl MPQP Device Handler Operation.

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