OR3C55-4PS240 查看數據表（PDF） - Agere -> LSI Corporation

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OR3C55-4PS240

ORCA® Series 3C and 3T Field-Programmable Gate Arrays

Agere -> LSI Corporation 

ORCA Series 3C and 3T FPGAs

Data Sheet

June 1999

Programmable Logic Cells (continued)

The GSRN signal is only asynchronous, and it sets/

resets all latches/FFs in the FPGA based upon the set/

reset configuration bit for each latch/FF. The set/reset

value determines whether GSRN and LSR are set or

reset inputs. The set/reset value is independent for

each latch/FF. A new option is available to disable the

GSRN function per PFU after initial device configura-

tion.

The latch/FF can be configured to have a data front-

end select. Two data inputs are possible in the front-

end select mode, with the SEL signal used to select

which data input is used. The data input into each

latch/FF is from the output of its associated LUT, F[7:0],

or direct from DIN[7:0], bypassing the LUT. In the front-

end data select mode, both signals are available to the

latches/FFs.

If either or both of these inputs is unused or is unavail-

able, the latch/FF data input can be tied to a logic 0 or

logic 1 instead (the default is logic 0).

The latches/FFs can be configured in three basic

modes:

1. Local synchronous set/reset: the input into the

PFU’s LSR port is used to synchronously set or

reset each latch/FF.

2. Local asynchronous set/reset: the input into LSR

asynchronously sets or resets each latch/FF.

3. Latch/FF with front-end select, LSR either synchro-

nous or asynchronous: the data select signal

selects the input into the latches/FFs between the

LUT output and direct data in.

For all three modes, each latch/FF can be indepen-

dently programmed as either set or reset. Figure 17

provides the logic functionality of the front-end select,

global set/reset, and local set/reset operations.

The ninth PFU FF, which is generally associated with

registering the carry-out signal in ripple mode func-

tions, can be used as a general-purpose FF. It is only

an FF and is not capable of being configured as a latch.

Because the ninth FF is not associated with an LUT,

there is no front-end data select. The data input to the

ninth FF is limited to the CIN input, logic 1, logic 0, or

the carry-out in ripple and half-logic modes.

F

DIN

LOGIC 1

LOGIC 0

LSR

GSRN

CD

CE/ASWE

CE

D

Q

s_set

F

DIN

LOGIC 1

LOGIC 0

s_reset

CLK

GSRN

LSR

SET RESET

CE/ASWE

CE

D

Q

F

DIN

LOGIC 1

LOGIC 0

CLK

SET RESET

GSRN

LSR

CD

SEL

CE/ASWE

CE

D

Q

DIN

CLK

SET RESET

CD

Key: C = configuration data.

Figure 17. Latch/FF Set/Reset Configurations

26

Lucent Technologies Inc.

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