User's Manual

22 Chapter3

Using HDLC.FRAME Protocol

Link State Indications

Non-E1/T1 ACC

If the “DSIG” configuration bit is set then the UP/DOWN state of the

HDLC.FRAME terminal is dependent on the state of the CTS and DCD

signals. When CTS and DCD are b oth asserted, the HDLC.FRAME

terminal is UP.

If the “DSIG” configuration bit is clear then the state of the

HDLC.FRAME terminal is not dependent on the state of the CTS and

DCD signals. In this case the H D LC.FRAME terminal is always UP.

E1/T1 ACC

The E1/T1 ACC determines the UP/DOWN state ofeach port by thestate

of the frame synchronization mechanism. When the hardware

establishes E1 or T1 frame synchronization on a port then all

HDLC.FRAME terminals on that port are immediately placed in the UP

state. If the hardware cannot detect received E1 or T1 frames without

error, then all HDLC.FRAME terminals on that port are placed in the

DOWN state. The sensitivity of the ACC to errors on the E1 or T1 lines is

affected by the “qdown” port option.

The “qdown” port configuration option is documented in the ACC

Utilities Guide chapter on TTGEN. It affects the way an E1 or T1 port is

set DOWN when frame synchronization is lost.

• Without the “qdown” option, the framesynchronizationofan E1 or T1

port is checked every second. If frame synchronization is lost at 4

consecutive checkpoints, then the port is set DOWN. This ensures

that higher level protocols are not disturbed by transient errors on

the line. This is the recommended configuration.