XRT74L74
4 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
REV. P1.1.1
PRELIMINARY
124
The remaining shaded bits are “Interrupt service” re-
lated and will be discussed in the following section.
3.2.2.6
Transmit Cell Processor Interrupt
Servicing
The Transmit Cell Processor generates interrupts up-
on the detection of an error in the “Data Path Integrity
Check” pattern.
If this condition occurs, and if that particular is en-
abled for interrupt generation, then the UNI will gener-
ate the “Data Path Integrity Check Pattern Error” in-
terrupt. Afterwards, when the local μP/μC reads the
UNI Interrupt Status Register, as shown below; it
should read “xxxxx1xxb” (where the b suffix denotes
a binary expression, and the “x” denotes a “don’t
care” value).
At this point, the local μC/μP has determined that the
Transmit Cell Processor block is the source of the in-
terrupt, and that the Interrupt Service Routine should
branch accordingly.
Since the Transmit Cell Processor contains only one
interrupt source, the Interrupt Service Routine, in this
case should perform a read of the “TxCP Control”
Register (Address = 60h) in order to verify and service
this condition. The bit format of this register is
presented below.
This register contain 8 active bit-fields. However, only
two of these bit-fields are relevant to Interrupt
Processing. Bit 0 is an Interrupt Status bit, and Bit 2 is
an Interrupt Enable bit.
Bit 2— TDPErrIntEn—“Test Data Path Integrity
Check” Interrupt Enable
This “Read/Write” bit-field is used to enable or disable
the “Data Path Integrity Check Pattern Error” inter-
rupt. Writing a “0” to this bit-field disables this inter-
rupt. Likewise, writing a “1” to this bit-field enables
this interrupt.
Bit 0—TDPErrIntStat—“Test Data Path Integrity
Check” Interrupt Status
This “Reset-upon-Read” bit-field indicates whether or
not the “Data Path Integrity Check Pattern Error” in-
terrupt has occurred since the last reading of the “Tx-
CP Control” Register. This interrupt will occur if the
Transmit Cell Processor detects a byte-pattern, in the
fifth octet position of each cell read from the TxFIFO,
that differs from the expected “Data Path Integrity
Check” pattern.
A “1” in this bit-field indicates that this interrupt has
occurred since the last reading of the “TxCP Control”
Register. A “0” in this bit-field indicates that this inter-
rupt has not occurred.
Note: Once the local μP has read this register, Bit 0
(TDPerr Interrupt Status) will be reset to “0”. Additionally, Bit
3 (TxCP Interrupt Status) within the “UNI Interrupt Status”
register will also be reset to “0”.
3.3
Transmit PLCP Processor
3.3.1
Brief Description of the Transmit
PLCP Processor
The Transmit PLCP Processor takes the incoming
cells (assigned, Idle, or OAM) from the Transmit Cell
Processor and packs them into PLCP frames. Each of
these PLCP frames also includes various overhead
UNI Interrupt Status Register (Address = 05h)
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 DS3
Interrupt
Status
Rx PLCP
Interrupt
Status
Rx CP
Interrupt
Status
Rx UTOPIA
Interrupt
Status
TxUTOPIA
Interrupt
Status
TxCP
Interrupt
Status
TxDS3
Interrupt
Status
One Sec
Interrupt
Status
RO
RO
RO
RO
RO
RO
RO
RO
0
x
x
x
1
x
x
x
Transmit Cell Processor Control Register (Address = 60h)
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Scrambler
Enable
Coset
Enable
HEC Insert
Enable
TDPChk
Pattern
GFC Insert
Enable
TDPErr
Interrupt
Enable
Idle Cell
HEC CalEn
TDPErr
Interrupt
Status
R/W
R/W
R/W
R/W
R/W
R/W
R/W
RUR