11 Communications Register

11 Communications Register

The Communications Register is used to set options pertaining to the clocks. The source and type of clock to be transmitted or received can be specified. External synchronization and RS-232 DTE test modes and can also be controlled with this register. The address of the Communications Register is Base+4. Table 9 details its bit definitions.

 

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

 

Bit 1

Bit 0

 

 

 

 

 

RLEN

 

 

 

 

 

 

 

TM ST

EXTSYNC

LLEN

or

RCKEN

TCKEN

 

0

0

 

 

 

 

 

SW_SYNC

 

 

 

 

 

 

 

 

Table 9 --- Communications Register - Read/Write

 

 

 

Bit 7:

TM ST --- Test Mode Status:

 

 

 

 

 

 

 

This bit can be used to read the status of the Test Mode signal on a DTE, allowing

 

the user to monitor the signal without generating any interrupts.

 

 

Bit 6:

EXTSYNC --- External Sync Enable:

 

 

 

 

 

 

If this bit is set (logic 1), software-controlled sync is disabled and the SCC's

 

SYNCA input is driven by the signal coming on pin 10 of the DB-25 connector.

Bit 5: LLEN --- Local Loopback Enable:

 

 

 

 

When set

 

(logic 1), this bit allows the DTE to test the functioning of the DTE/DCE interface

 

and the transmit and receive sections of the local DCE. The DCE device must

 

support local loopback for this to work. When cleared (logic 0), no testing occurs.

 

LLEN can also be used as a software-controlled general-purpose output.

Bit 4: RLEN --- Remote Loopback Enable:

 

 

 

 

SW_SYNC

 

--- Software Sync On:

 

 

 

 

 

 

When

the 'C' option is used with the client driver or enabler, this bit functions as SW_SYNC, otherwise it functions as RLEN.

RLEN

('C' option not used)If this bit is set (logic 1), the DTE can test the transmission path through the remote DCE to the remote DTE interface and the return transmission path. The remote device must support remote loopback for this to work. When cleared (logic 0), no testing occurs.

SW_SYNC ('C' option is used)

This bit is used to drive the active-low SYNC input of the channel A receiver. The SYNC signal is asserted when this bit is set (logic 1), and is deasserted when this bit is clear (logic 0). This is useful in situations where it is necessary to

Page 44
Image 44
Quatech MPAP-100 user manual Communications Register, Swsync