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DS33R11 Ethernet Mapper with Integrated T1/E1/J1 Transceiver
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10.5 E1 Framer/Formatter Control and Status
The E1 framer portion of the transceiver is configured by a set of four control registers. Typically, the control
registers are only accessed when the system is first powered up. Once the device has been initialized, the control
registers need only to be accessed when there is a change in the system configuration. There are two receive
control registers (TR.E1RCR1 and TR.E1RCR2) and two transmit control registers (TR.E1TCR1 and TR.E1TCR2).
There are also four status and information registers. Each of these eight registers is described in this section.
Table 10-3. E1 Sync/Resync Criteria
FRAME OR
MULTIFRAME
LEVEL
SYNC CRITERIA RESYNC CRITERIA ITU SPEC.
FAS
FAS present in frame N and
N + 2; FAS not present in
frame N + 1
Three consecutive incorrect
FAS received
Alternate: (TR.E1RCR1.2 = 1)
The above criteria is met or
three consecutive incorrect bit
2 of non-FAS received
G.706
4.1.1
4.1.2
CRC4
Two valid MF alignment
words found within 8ms
915 or more CRC4 codewords
out of 1000 received in error
G.706
4.2 and 4.3.2
CAS
Valid MF alignment word
found and previous time slot
16 contains code other than
all 0s
Two consecutive MF alignment
words received in error
G.732
5.2