PA7540 Datasheet, PDF (3/10 Pages) Anachip Corp – PA7540 PEEL Array Programmable Electrically Erasable Logic Array

Sum-A = D, T, J or Sum-A
Sum-B = Preset, K or Sum-B
Sum-C = Reset, Clock, Sum-C
Sum-D = Clock, Output Enable
P
D
Q
R
D Register
Q = D after clocked
Best for storage, simple counters,
shifters and state machines with
few hold (loop) conditions.
P
T
Q
R
T Register
Q toggles when T = 1
Q holds when T = 0
Best for wide binary counters (saves
product terms) and state machines
with many hold (loop) conditions.
P
J
Q
KR
JK Register
Q toggles when J/K = 1/1
Q holds when J/K = 0/0
Q = 1 when J/K = 1/0
Q = 0 when J/K = 0/1
Combines features of both D and T
registers.
08-14-005A
Figure 5. LCC Register Types
SUM-A can serve as the D, T, or J input of the register or a
combinatorial path. SUM-B can serve as the K input, or the
preset to the register, or a combinatorial path. SUM-C can
be the clock, the reset to the register, or a combinatorial
path. SUM-D can be the clock to the register or the output
enable for the connected I/O cell. Note that the sums
controlling clocks, resets, presets and output enables are
complete sum-of-product functions, not just product terms
as with most other PLDs. This also means that any input or
I/O pin can be used as a clock or other control function.
Several signals from the global cell are provided primarily
for synchronous (global) register control. The global cell
signals are routed to all LCCs. These signals include a
high-speed clock of positive or negative polarity, global
preset and reset, and a special register-type control that
selectively allows dynamic switching of register type. This
last feature is especially useful for saving product terms
when implementing loadable counters and state machines
by dynamically switching from D-type registers to load and
T-type registers to count (see Figure 10).
Multiple Outputs Per Logic Cell
An important feature of the logic control cell is its capability
to have multiple output functions per cell, each operating
independently. As shown in Figure 4, two of the three
outputs can select the Q output from the register or the
Sum A, B or C combinatorial paths. Thus, one LCC output
can be registered, one output can be combinatorial and the
third, an output enable. The multi-function PEEL™ Array logic
cells are equivalent to two or three macrocells of other PLDs,
which have only one output per cell. They also allow registers
to be truly buried from I/O pins without limiting them to input-
only (see Figure 8 ).
From Global Cell
I/O Cell Clock
To
Array
Input
MUX
REG/
Latch
Q
From
Logic
Control
Cell
A,B,C
or
Q
D
MUX
MUX
10
7540 /O Cell (IOC)
Figure 6. I/O Cell Block Diagram
I/O Pin
08-14-006A
D
Q
IO C R egister
Q = D after rising edge of clock
holds until next rising edge
L
Q
IO C Latch
Q = L when clock is high
holds value when clock is low
08-14-007A
Figure 7. IOC Register Configurations
I/O Cell (IOC)
All PEEL™ Arrays have I/O cells (IOC) as shown above in
Figure 6. Inputs to the IOCs can be fed from any of the LCCs
in the array. Each IOC consists of routing and control
multiplexers, an input register/transparent latch, a three-state
buffer and an output polarity control. The register/ latch can
be clocked from a variety of sources determined by the global
cell. It can also be bypassed for a non-registered input. The
combination of LCC and IOC allows for multiple buried
registers and logic paths. (See Figure 8).
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04-02-051B