OR3T125 Agere Systems, OR3T125 Datasheet - Page 56

• Manufacturer Part Number: OR3T125
• Description: 3C and 3T Field-Programmable Gate Arrays
• Manufacturer: Agere Systems

ORCA Series 3C and 3T FPGAs
Special Function Blocks
Start-Up Logic
The start-up logic block is located in the lower right cor-
ner of the FPGA. This block can be configured to coor-
dinate the relative timing of the release of GSRN, the
activation of all user I/Os, and the assertion of the
DONE signal at the end of configuration. If a start-up
clock is used to time these events, the start-up clock
can come from CCLK, or it can be routed into the start-
up block using lower right corner routing resources.
These signals are described in the Start-Up subsection
of the FPGA States of Operation section.
Clock Control (CLKCNTRL) and StopCLK
There is one CLKCNTRL block in the MID section of
the interquad routing on each side of the FPGA. This
block is used to selectively distribute the fast clock to
the PLC array and the left (top) and right (bottom)
ExpressCLKs (ECKL and ECKR) to the side of the
array on which the CLKCNTRL block resides.
Notes:
CLKCNTRL output clocks are ExpressCLK left and right and fast clock.
Clock shutoff shown active-high acting on clock falling edge.
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CLKCNTRL OUTPUT
CLOCK SHUTOFF
CLOCKS
EXPRESSCLK LEFT
Figure 35. Top CLKCNTRL Function Block
(continued)
OFF_SET
FAST CLOCK
OFF_HLD
The source clock for the CLKCNTRL block comes
either from the ExpressCLK pad at the middle of the
side of the FPGA or from the corner ExpressCLK route
that comes from the corner ExpressCLK pad (at the
lower left or upper right of the device, whichever is
closer). The programmable clock manager ExpressCLK
output can also be sourced to this corner routing for
distribution at the two closest CLKCNTRL blocks.
Each CLKCNTRL block also features an invertible
StopCLK shutoff input that is available from local rout-
ing. This feature may be used to glitchlessly stop and
start the clock at the three outputs of each CLKCNTRL
block and has the option of doing so on either the rising
or falling edge of the clock. When the clock is halted
based on its rising edge, it stops and stays at V
When it is stopped based on its falling edge, it stops
and stays at GND. If the StopCLK shutoff signal meets
the CLKCNTRL setup and hold times, the clock is
stopped on the second clock cycle after the shutoff sig-
nal. A diagram of the bottom CLKCNTRL block and
StopCLK timing is shown in Figure 35.
EXPRESSCLK RIGHT
CORNER EXPRESSCLK
CLOCK SHUTOFF
OFF_SET
Lucent Technologies Inc.
OFF_HLD
Data Sheet
June 1999
DD
5-5981(F)
.