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PMC-Sierra, Inc.
PM73488 QSE
L
PMC-980616
Issue 3
5 Gbit/s ATMSwitch Fabric Element
Released
Datasheet
74
6.4.3
QSE Interface Signals
Table 18. QSE Interface Signals (364 Signal Pins)
Signal Name
Ball
#
# of
Pins
Type
Description
CELL_START
J6
1
In
The rising edge of
Cell Start
indicates to the QSE it should
stop looking for the SE_SOC_IN(31:0) on the input ports.
The signal must have the following characteristics: The
rising edge should come every 118 clocks exactly. Also, it
must be high for at least one clock and low for at least eight
clocks during each 118-cycle period. Thus,
Cell Start
must
be high for x clocks and low for (118-x) clocks, where
1
≤
x
≤
110.
Cell 24 Start
indicates the start of the 4N
th
cell time. It
should be driven high every 4N
th
CELL_START
assertions, and should match CELL_START when driven
high. Here, N can be any integer
≥
1, as long as it is the
same for all the QSE and QRT devices in the fabric. It is
called CELL_24_START because N used to be 6 (so 4N
used to be 24) in some legacy systems, but that is no longer
relevant.
CELL_24_START
C2
1
In
CTRL_IN
(or /No_Data_Out)
E2
1
In
Control In is used to feed in an information packet to the
QSE. This information packet can be used to tell the QSE
not to accept any incoming cells (which is called a “/No
Data In” command) and/or tell it not to send any cells to
the next stage (which is called a “/No Data Out”
command).
There is a software configurable mode which splits the
“/No Data In” and “/No Data Out” functionality and
assigns them to separate pins. If this mode is turned on,
then the CTRL_IN pin performs the “/No Data Out”
functionality. (The complementary function of “/No Data
In” is performed by the STAT_OUT pin; see below.) That
is, whenever CTRL_IN is pulled low, the QSE will not
send any cells to the next stage.
After Reset, the above mode is on by default; that is, the
CTRL_IN pin is configured as “/No Data Out”.