8K x 8 Registered PROM
CY7C265
Cypress Semiconductor Corporation • 3901 North First Street • San Jose • CA 95134 • 408-943-2600
April 1988 – Revised April 1995
1CY7C26 5
Features
• CMOS for optimum speed/power
• High speed (commercial and military)
—15 ns address set-up
—12 ns clock to output
• Low power
—660 mW (commercial)
—7 70 mW (mi litary)
• On-chip edge-triggered re gisters
—Ideal for pipelined micro programme d system s
• EPROM technology
—100% programmable
—Reprogrammable (7C265W)
• 5V ±10% VCC, commercial and military
• Capable of withsta nding >2001V static discharge
• Slim 28-pin, 300-mil plastic or hermet ic DIP
Functio nal D escription
The CY7C265 is a 8192 x 8 registered PROM. It is organized
as 8,192 word s by 8 bits wid e, and has a pipeline output reg-
ister . In addition, the device features a programmable initialize
byte that may be loaded into the pipelin e register with the ini-
tiali ze signal. The programmable initiali ze byte is the 8,193rd
byte in the PROM and its value is programmed at the time of
use.
Packaged in 28 pins, the PROM has 13 address signals (A0
through A12), 8 data out signals (O0 through O 7), E/I (enable
or initialize), and CLOCK.
CLOCK functions as a pipeline clock, loading the c ontents of
the addressed memory location into the pipeline register on
each rising edge. The data will appear on the outputs if th ey
are enabled. One pin on the CY7C265 is programmed to per-
form either the enable or the initialize function.
If the asynch ronous enable (E) is being used, the outputs may
be disabled at any time by switching the enable to a logic
HIGH, and may be returned to the active state by switching the
enable to a logic LOW.
If the synchronous enable (ES) is being us ed, the outputs will
go to the OFF or high-imped ance s tate up on the next positive
clock edge after the synchronous enabl e input is switched to
a HIGH level. I f the synchronous enable pin is switched to a
logic LOW, the subsequent positive clock edge will return the
output to the active state. Following a positive cloc k edge, the
address a nd synchronous enable inputs are free to change
since no change in the output will occur until the next
LOW-to-HIG H tran sition of the clock. Thi s unique feature al-
lows the CY7C265 decoders and sense amplifiers to access
the next location while previously a ddressed data remains sta-
ble on the outputs.
If the E/I pi n is used for INIT (asynchronous), then the outputs
are permanently enabled. The init ialize function is useful dur-
ing power-up and time-out sequences, and can facilitate im-
plementation of other sop histicated functions such as a b ui lt -in
“jump start” address. When activated, the i nitialize control in-
put causes the contents of a user programmed 8193rd 8-bit
word to be loaded into the on-chip register. Each bit is pro-
gr ammable and the ini tialize function can be used to load any
desired combination of 1’s a nd 0’s into the register. In the un-
programmed state, activating INIT will generate a register
clear (all outputs LOW). If all the bits of the initialize word are
programmed to be a 1, activating INIT performs a register pre-
set (all outputs HIGH).
Applying a LOW to the INIT i nput causes an immediate load
of the programmed initialize word into the pipeline register and
onto the outputs. The INIT LOW disables cl ock and m ust re-
turn HIGH to enable clock independent of all other inputs, in-
cluding the clock.