ACC HDLC-NRM (SDLC) User's Guide

SDLC Loop Mode Option

Introduction

Appendix B62

Introduction

The SDLC loop mode of operation is described in the IBM document

“Synchronous Data Link Control General Information” GA27-3093. A

subset of this standard has been implemented. Only the primary station

is supported in loop mode. The “turn-around” signal described in the

SDLC document is not used.

NOTE The SDLC loop mode is not available for use on the 2-Channel ACC

interface.

Frame Types Supported

In loop mode the HDLC/NRM protocol supports the use of the following

additional commands and responses:

Request to Send Control

In Primary/Loop mode the HDLC/NRM protocol maintains the RTS

signal in the ON condition.

Unnumbered Poll

In Primary/Loop mode the HDLC/NRM protocol will poll the secondary

stations with the Unnumbered Poll (UP) command with the P bit set to

‘0’ and with the address field set to 0xFF.

Commands Responses

SIM RIM

TEST TEST