User`s manual

10 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.
00TCKENRCKEN
RLEN
or
SW_SYNC
LLENEXTSYNCTM ST
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
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.
Quatech MPAC-100 User's Manual
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