PALCE26V12 Datasheet, PDF (5/21 Pages) Advanced Micro Devices – 28-Pin EE CMOS Versatile PAL Device

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The feedback multiplexer is controlled by the same bit
(S1) that controls whether the output is registered or
combinatorial, as on the 22V10, with an additional
control bit (S3) that allows the alternative feedback path
to be selected. When S3 = 1, S1 selects register
feedback for registered outputs (S1 = 0) and I/O
feedback for combinatorial outputs (S1 = 1). When S3 =
0, the opposite is selected: I/O feedback for registered
outputs and register feedback for combinatorial outputs.
Programmable Enable and I/O
Each macrocell has a three-state output buffer con-
trolled by an individual product term. Enable and disable
can be a function of any combination of device inputs or
feedback. The macrocell provides a bidirectional I/O pin
if I/O feedback is selected, and may be configured as a
dedicated input if the buffer is always disabled. This is
accomplished by connecting all inputs to the enable
term, forcing the AND of the complemented inputs to be
always LOW. To permanently enable the outputs, all
inputs are left disconnected from the term (the
unprogrammed state).
Programmable Output Polarity
The polarity of each macrocell output can be active high
or active low, either to match output signal needs or to
reduce product terms. Programmable polarity allows
Boolean expressions to be written in their most compact
form (true or inverted), and the output can still be of the
desired polarity. It can also save “DeMorganizing”
efforts.
Selection is controlled by programmable bit S0 in the
output macrocell, and affects both registered and
combinatorial outputs. Selection is automatic, based on
the design specification and pin definitions. If the pin
definition and output equation have the same polarity,
the output is programmed to be active high.
Preset/Reset
For initialization, the PALCE26V12 has additional
Preset and Reset product terms. These terms are
connected to all registered outputs. When the Synchro-
nous Preset (SP) product term is asserted high, the
output registers will be loaded with a HIGH or the next
LOW-to-HIGH clock transition. When the Asynchronous
Reset (AR) product term is asserted high, the output
registers will be immediately loaded with a LOW
independent of the clock.
Note that preset and reset control the flip-flop, not the
output pin. The output level is determined by the output
polarity selected.
Power-Up Reset
All flip-flops power up to a logic LOW for predictable
system initialization. Outputs of the PALCE26V12 will
be HIGH or LOW depending on whether the output is
active low or active high, respectively. The VCC rise must
be monotonic, and the reset delay time is 1000 ns
maximum.
Register Preload
The register on the PALCE26V12 can be preloaded
from the output pins to facilitate functional testing of
complex state machine designs. This feature allows
direct loading of arbitrary states, thereby making it
unnecessary to cycle through long test vector se-
quences to reach a desired state. In addition, transitions
from illegal states can be verified by loading illegal
states and observing proper recovery.
Security Bit
After programming and verification, a PALCE26V12
design can be secured by programming the security bit.
Once programmed, this bit defeats readback of the
internal programmed pattern by a device programmer,
securing proprietary designs from competitors. Pro-
gramming the security bit disables preload, and the
array will read as if every bit is disconnected. The
security bit can only be erased in conjunction with
erasure of the entire pattern.
Programming and Erasing
The PALCE26V12 can be programmed on standard
logic programmers. It also may be erased to reset a
previously configured device back to its virgin state.
Erasure is automatically performed by the programming
hardware. No special erase operation is required.
Quality and Testability
The PALCE26V12 offers a very high level of built-in
quality. The erasability of the device provides a means
of verifying performance of all AC and DC parameters.
In addition, this verifies complete programmability and
functionality of the device to provide the highest
programming yields and post-programming functional
yields in the industry.
Technology
The high-speed PALCE26V12 is fabricated with AMD’s
advanced electrically erasable (EE) CMOS process.
The array connections are formed with proven EE cells.
Inputs and outputs are designed to be compatible with
TTL devices. This technology provides strong input
clamp diodes, output slew-rate control, and a grounded
substrate for clean switching.
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PALCE26V12 Family