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Table 21. STS-3c/STM-1 configuration for RX_FRAME_POSITION [3:0]
Data on RX_DATA[7:0] RX_FRAME_POSITION[3:0]
last byte of frame 0000
first A1 byte 0001
second A1 byte 0010
third A1 byte 0011
first A2 byte 0100
second A2 byte 0101
third A2 byte 0110
J0 byte 0111
first Z0 byte 1000
last Z0 byte 1001
first byte after last Z0 byte 1010
second byte after last Z0 byte 1011
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Bit name Reserved Reserved RX_LAIS RX_LRDI Reserved K1_UNSTAB S1_UNSTAB J0_OOF
R/W ——RR— RR R
Value 001000 0 1
after
reset
ADDR=0x102: Receive LOH Status
Bits 7-6: Reserved
Bit 5: RX_LAIS: It will be asserted after the three LSBs of the received K2 byte are received as 111 for the
number of consecutive frames specified in the K2_CONSEC_NUM [3:0] register. It will be de-
asserted after the three LSBs of the received K2 byte are not received as 111 for the number of
consecutive frames specified in the K2_CONSEC_NUM [3:0].
Bit 4: RX_LRDI: It will be asserted after the three LSBs of the received K2 byte are received as 110 for
the number of consecutive frames specified in the K2_CONSEC_NUM [3:0] register. It will be de-
asserted after the three LSBs of the received K2 byte are not received as 110 for the number of
consecutive frames specified in the K2_CONSEC_NUM [3:0].
Bit 3: Reserved
Bit 2: K1_UNSTAB: This bit is used to check for instability for K1 byte. Set if no three consecutive
frames are received with identical K1 bytes for 12 successive frames.
Bit 1: S1_UNSTAB: The S1 LSB is checked for instability. If, for 12 successive frames, three consecutive
frames are not received with identical S1 LSB in SDH mode, or eight consecutive frames are not
received with identical S1 in SONET mode, the S1_UNSTAB bit is asserted. It is deasserted when
the required number of identical S1 LSBs are received.