
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
118
3.3.2.116
PMON CP Bit Error Count Register (MSB)
This “Reset-upon-Read” register, along with the “PMON
CP Bit Error Count—LSB” register (Address = 75h)
contains a 16 bit representation of the number of CP
Bit Errors that have been detected by the Receive
DS3 Framer, since the last read of these register.
This register contains the MSB (or Upper Byte) value
of this 16-bit expression.
3.4
The “Loss of Clock Enable” Feature
The timing for the Microprocessor Interface section
originates from a 44.736 MHz signal that is provided
by either the TxInClk or the RxLineClk signals. How-
ever, if the UNI device experiences a “Loss of Clock
signal” event such that neither the TxInClk nor the
RxLineClk signal are present, then the UNI Micropro-
cessor Interface section ceases to function.
The UNI device offers a “Loss of Clock” (LOC) protec-
tion feature that allows the Microprocessor Interface
section to at least complete or terminate an “in-process”
Read or Write cycle (with the local μP) should this
“Loss of Clock” event occur. The “LOC” circuitry
consists of a ring oscillator that continuously checks
for signal transitions at the TxInClk and RxLineClk
input pins. If a “Loss of Clock Signal” event occurs
such that no transitions are occurring on these pins,
then the LOC circuitry will automatically assert the
Rdy_Dtck signal in order to complete (or terminate)
the current “Read” or “Write” cycle with the UNI
Microprocessor Interface section.
The user may enable or disable this “LOC Protection”
feature by writing to Bit 7 (LOC Enable) within the
UNI I/O Register, as depicted below.
Writing a “1” to this bit-field enables this “LOC
Protection” feature. Writing a “0” to this bit-field
disables this feature.
Note:
The “Ring Oscillator” can be a source of noise,
within the UNI chip. Hence, there may be situations where
the user will wish to disable the “LOC Protection” feature.
3.5
Using the PMON Holding Register
If the Microprocessor Interface section is configured
to operate over an 8-bit data bus, then the local μP
will be able to read from and write to the UNI on-chip
registers, 8 bit per (read or write) cycle. Since most of
the UNI on-chip registers contain 8-bits, communicating
with the local μP over an 8-bit data bus, is not much of
Address = 74h, PMON CP Bit Error Count—MSB
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Rx CP Bit Error Count—Upper Byte
RUR
RUR
RUR
RUR
RUR
RUR
RUR
RUR
0
0
0
0
0
0
0
0
Address = 72h, Line Interface Drive Register
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
REQB
TAOS
Encodis
TxLev
RLoop
LLoop
RO
RO
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
Address = 01h, UNI I/O Control Register
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
LOC Enable
Test
PMON
Interrupt
Enable Reset
AMI/B3ZS*
Unipolar/
Bipolar*
TxLine
Clk Inv
RxLine
Clk Inv
Reframe
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0