PM6341 E1XC
DATA SHEET
PMC-910419
ISSUE 8
E1 FRAMER/TRANSCEIVER
Register 0EH: E1XC Phase Status Word (LSB)
Bit
Type
Function
Default
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
PSB[7]
PSB[6]
PSB[5]
PSB[4]
PSB[3]
PSB[2]
PSB[1]
PSB[0]
X
X
X
X
X
X
X
X
This register contains the least significant byte, PSB[7:0], of the 9-bit phase
status word.The 9-bit phase status word indicates the relative phase difference
between the received E-1 line timing (available on RCLKO) and system timing.
By utilizing the value of the phase status word, the system timing can be locked
to the receive line timing via an external software controlled phase-locked-loop.
The least significant 8 bits contained in this register indicate a count value (0-
255) of the number of system backplane clock cycles between successive 125µs
frame pulses.The most significant 5 bits (PSB[7:3]) represent a time slot number
(0-31) and the least significant 3 bits (PSB[2:0]) represent the bit number within
the timeslot (0-7). The count value corresponds to the location within the system
frame where the receive line-timed frame pulse occurred. If the received line
clock frequency is higher on average than the system clock frequency, the phase
status word value will be seen to decrease during successive register reads. If
the received line clock frequency is lower on average than the system clock
frequency, the phase status word value will be seen to increase during
successive register reads.
The 9th bit of the Phase Status Word indicates the "frame count" and will toggle
when two successive 8-bit counter values straddle a frame boundary.The
PSB[8] bit will toggle when the bit and timeslot count indicated by PSB[7:0]
exceeds timeslot 31, bit 7 or the count goes below timeslot 0, bit 0. This is
determined by comparing the PSB[7:6] bits of the current phase status word
value to those of the previous word value; PSB[8] is toggled only under the
following conditions (all other bit value transitions leave PSB[8] unchanged):
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
99
PMC [ PMC-SIERRA, INC ]
