DS3171/DS3172/DS3173/DS3174
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Bit 4: LOOP Time Enable (LOOPT).
When this bit is set, the port is in loop time mode. The transmit clock is set to
the receive clock from the RLCLKn pin or the recovered clock from the LIU or the CLAD clock
and the TCLKIn pin
is not used. This function of this bit is conditional on other control bits. See
Table 10-4
for more details.
0 = Normal transmit clock operation
1 = Transmit using the receive clock
Bit 3: CLAD Transmit Clock Source Control (CLADC).
This bit is used to enable the CLAD clocks as the source
of the internal transmit clock. This function of this bit is conditional on other control bits. See
Table 10-4
for more
details.
0 = Use CLAD clocks for the transmit clock as appropriate
1 = Do not use CLAD clocks for the transmit clock – (if no loopback is enabled, TCLKIn is the source)
Bit 2: Receive Framer IO Signal Timing Select (RFTS).
This bit controls the timing reference for the signals on
the receive framer interface IO pins. The pins controlled are RSERn, RSOFOn / RDENn. See
Table 10-8
for more
details.
0 = Use output clocks for timing reference
1 = Use input clocks for timing reference
Bit 1: Transmit Framer IO Signal Timing Select (TFTS).
This bit controls the timing reference for the signals on
the transmit framer interface IO pins. The pins controlled are TSOFIn, TSERn, and TSOFOn / TDENn. See
Table
10-7
for more details.
0 = Use output clocks for timing reference
1 = Use input clocks for timing reference
Bit 0: Transmit Line IO Signal Timing Select (TLTS).
This bit controls the timing reference for the signals on the
transmit line interface IO pins. The pins controlled are TPOSn / TDATn and TNEGn. See
Table 10-6
for more
details.
0 = Use output clocks for timing reference
1 = Use input clocks for timing reference
Register Name:
PORT.CR4
Register Description:
Port Control Register 4
Register Address:
(0,2,4,6)46h
Bit #
15
14
13
12
Name
--
--
--
--
Default
0
0
0
0
Bit #
7
6
5
4
Name
GPIOB3
GPIOB2
GPIOB1
GPIOB0
Default
0
0
0
0
11
10
9
8
RESERVED
0
3
GPIOA3
0
LBM2
0
2
GPIOA2
0
LBM1
0
1
GPIOA1
0
LBM0
0
0
GPIOA0
0
Bits 10 to 8: Loopback Mode [2:0] (LBM[2:0]).
These bits select the loopback modes for analog loopback (ALB),
line loopback (LLB), payload loopback (PLB) and diagnostic loopback (DLB). See
Table 10-17
for the loopback
select codes. Default: No Loopback.
LBM[2:0]
000
001
010
011
10X
110
111
ALB
0
1
0
0
0
0
0
LLB
0
0
1
0
0
1
0
PLB
0
0
0
1
0
0
0
DLB
0
0
0
0
1
1
1