AK2540 Datasheet, PDF (20/33 Pages) Asahi Kasei Microsystems – Quad T1 Transceiver

ASAHI KASEI
[AK2540]
Loopbacks (Hardware Mode and Host Mode)
Local Loopback (LLOOP) in channel x is selected when LLOOPx is “high” and RLOOPx is “low”.
In LLOOP mode, the receiver circuits are inhibited. The transmit clock and data inputs (TCLK
and TOPS/TNEG) are looped back and output at RCLK and RPOS/RNEG.
The transmitter circuits are unaffected by LLOOP.
Remote Loopback (RLOOP) in channel x is selected when RLOOPx is “high” and LLOOPx is “low”.
However, RLOOP is ignored if AIS is selected. In RLOOP mode, the transmit clock and data inputs
(TCLK and TPOS/TNEG) are ignored. The RPOS/RNEG outputs are looped back to the transmit
circuits and output on TTIP and TRING at the RCLK frequency. Receiver circuits are unaffected
by the RLOOP and continue to output the data and clock signals received from the line.
Table 4. Loopback mode Selection
RLOOPx
0
0
1
1
LLOOPx
0
1
0
1
Function
Normal
Local Loop back
Remote Loop back
Reserved (NA)
Driver Performance Monitor (Host Mode)
The device incorporates an internal Driver Performance Monitor (DPM) in parallel with TTIP and
TRING. DPMx is set “high” when DPM detect 320 bits of consecutive space in channel x. INT
pin becomes “high” when DPMx is set “high”, if MDPMx is “low”. DPMx registers represent the
current status regardless of the MDPMx status. DPMx returns to “low”, when a mark is detected.
However, DPMx is to be kept “high” for 320 TCLK cycle after the first detection of the event.
DPM output is ignored when all “0” AIS is being transmitted
Line Short Protection Circuit
The transmit driver includes a line short protection circuit. When the line short protection circuit
detect a line short, transmit signal is fixed to “space”. The line short protection circuit monitor the
line short every 160bits cycle. (This alarm is not outputted. Line short is shown for Driver Failure
described below.)
MS0012-E-00
20
2000/1