
XRT74L73
3 CHANNEL, ATM UNI/PPP DS3/E3 FRAMING CONTROLLER
PRELIMINARY
REV. P1.0.1
156
tents of the GFC Nibble-field for each cell that it re-
ceives, via the “GFC Nibble Field” serial output port.
The “Receive GFC Nibble-Field” serial output port
consists of the following pins.
RxGFC
RxGFCClk
RxGFCMSB
The data is output via the RxGFC output pin. The or-
der of transmission, within a given cell, is with the
MSB first and in descending order until transmitting
the LSB bit. Afterwards, the “GFC Nibble-field” serial
output port will output the MSB for the GFC Nibble-
field of the next cell. This data is clocked out on the
rising edge of the RxGFCClk output signal. The RxG-
FCMSB output pin will be pulsed “high” each time the
MSB of the GFC Nibble field, for a given cell, is
present at the RxGFC input. Figure 34 presents an il-
lustration depicting the behavior of the RxGFC Serial
Output Port signals.
3.3.2.8Receive Cell Processor Interrupts
The Receive Cell Processor will generate interrupts
upon
HEC Errors
OAM Cell received
Loss of Cell Delineation
If one of these conditions occur, and if that particular
condition is enabled for interrupt generation, then
when the local μC/μP reads the UNI Interrupt Status
Register, as shown below, it should read ‘xx1xxxxxb’
(where the -b suffix denotes a binary expression, and
‘x’ denotes a “don’t care” value).
At this point, the local μC/μP will have determined that
the Receive Cell Processor block is the source of the
interrupt, and that the Interrupt Service Routine
should branch accordingly. In order to accomplish this
the local μC/μP should now read the “RxCP Interrupt
Status Register” (Address = 4Fh). The bit format of this
register is presented below.
F
IGURE
34. I
LLUSTRATION
OF
THE
B
EHAVIOR
OF
THE
R
X
GFC S
ERIAL
O
UTPUT
P
ORT
SIGNALS
RxGFCClk
RxGFCMSB
t52
RxGFC
BIT 3
BIT 2
BIT 1
BIT 0
t50
t48
t51
t47
t49
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
RxDS3
Interrupt
Status
RxPLCP
Interrupt
Status
RxCP
Interrupt
Status
RxUTOPIA
Interrupt
Status
TxUTOPIA
Interrupt
Status
TxCP
Interrupt
Status
TxDS3
Interrupt
Status
One Sec Inter-
rupt
Status
RO
RO
RO
RO
RO
RO
RO
RUR
x
x
1
x
x
x
x
x