Philips Semiconductors Programmable Logic Devices
Product specification
ECL programmable array logic
10H20EV8/10020EV8
D
AP
D
AP
D
Q
D
Q
CK
Q
AR
CK
Q
AR
Registered Active-HIGH
Registered Active-LOW
D
D
Combinatorial Active-HIGH
Figure 2.
Combinatorial Active-LOW
Output Macro Cell Configurations
Active-HIGH and Active-LOW, a Preset
signal will force the Active-HIGH outputs
HIGH while the Active-LOW outputs would go
LOW, even though the Q output of all
flip-flops would go HIGH. A Reset signal
would force the opposite conditions.
OUTPUT MACRO CELL
CONFIGURATION
Shown in Figure 2 are the four possible
configurations of the output macrocell using
fuses S
0
and S
1
. As seen, the output can
either be registered Active-HIGH/LOW with
feedback or combinatorial Active-HIGH/LOW
with feedback. If the registered mode is
chosen, the feedback from the Q output to
the AND array enables one to make state
machines or shift registers without having to
tie the output to one of the inputs. If a
combinatorial output is chosen, the feedback
gate is enabled from the pin and allows one
to create permanent outputs, permanent
inputs, or I/O pins through the use of the
output enable (D) product term.
controlled by a programmed pattern. A HIGH
on the D term enables the output, while a
LOW performs the disable function. Output
enable control can be achieved by
programming a pattern on the D term.
The output enable control can also be used
to expand a designer’s possibilities once a
combinatorial output has been chosen. If the
D term is always HIGH, the pin becomes a
permanent Active-HIGH/LOW output. If the
D term is always LOW (all fuses left intact),
the pin now becomes an extra input.
PRELOAD
To simplify testing, the 10H20EV8/10020EV8
has also included PRELOAD circuitry. This
allows a user to load any particular data
desired into the registers regardless of the
programmed pattern. This means that the
PRELOAD can be done on a blank part and
after that same part has been programmed to
facilitate any post-fuse testing desired.
It can also be used by a designer to help
debug a circuit. This could be important if a
state machine was implemented in the
10H20EV8/ 10020EV8. The PRELOAD
would allow the entry of any state in the
sequence desired and start clocking from that
particular point. Any or all transitions could be
verified.
PRESET AND RESET
The 10H20EV8/10020EV8 also includes a
separate product term for asynchronous
Preset and asynchronous Reset. These lines
are common for all registers and are asserted
when the specific product term goes HIGH.
Being asynchronous, they are independent of
the clock. It should be noted that the actual
state of the output is dependent on how the
polarity of the particular output has been
chosen. If the outputs are a mix of
OUTPUT ENABLE
Each output on the 10H20EV8/10020EV8
has its own individual product term for output
enable. The use of the D product term
(direction control) allows the user three
possible configurations of the outputs. They
are: always enabled, always disabled, and
October 22, 1993
117
PHILIPS [ NXP SEMICONDUCTORS ]
