CY7C261
CY7C263/CY7C264
Document #: 38-04010 Rev. ** Page 5 of 16
Erasure Characteri stics
W ave lengths of lig ht less than 400 0 angstroms begi n to erase
the devices in the windowed package. For this reason, an
opaque label should be placed over the window if the PROM
is exposed to sunlight or fluorescent lighting for extended pe-
riods of time.
The recommended dose of ultraviolet light for erasure is a
wavel ength of 2537 angstro ms for a minimum dos e (UV inten-
sity multiplied by exposure time) of 25 Wsec/cm2. For an ultra -
violet lamp with a 12 mW/cm2 power rating, the exposure time would
be approximately 35 minutes. The 7C261 or 7C263 needs to
be within 1 inch of the lamp during erasure. Permanent dam-
age may result if the PROM is exposed to high-intensity UV
light for an extended period of time. 7258 Wsec/cm2 is the
recommended maximum dosage.
Operating Modes
Read
Read is the normal operating mode for programmed device. In
this mode, all signals are normal TTL levels. The PROM is
addressed with a 13-bit field, a chip select, (active LOW), is
applied to the CS pin, and th e contents of th e addr essed loca tio n
appear on the data out pins.
Program, Program Inhibit, Program Verify
These m odes are e ntered by pl acing a hi gh v oltage VPP on pin
19, with pins 18 a nd 20 set to VILP. In thi s sta te, pin 21 b ecomes a
latch sign al, allo win g the upper 5 add res s bits to be lat ched into an
onboard r egister, pin 22 be comes an act ive LOW pro gram (PGM)
signal and pin 23 becomes an active LOW verify (VFY) signal. Pins
22 and 23 should never be active LOW at the same time. The PRO-
GRAM mode exists when PGM is LOW, and VFY is HIGH. The verify
mode exists when the reverse is true, PGM HIGH and VFY LOW and
the program inhibit mode is entered with both PGM and VFY HIGH.
Program inhibit is specifically provided to allow data to be placed on
and removed from the data pins without conflict
Swit c h ing Waveforms[4]
tAA
VCC
SUPPLY
CURRENT
A0-A
12
ADDRESS
CS
tPU
O0-O
7
tHZCS tACS
50% 50%
tPD
Table 1. Mode Selection
Pin Function[6, 7]
Read or Output Disable A12 A11 A10 A9A8CS O7–O0
Mode Program NA VPP LATCH PGM VFY CS D7–D0
Read A12 A11 A10 A9A8VIL O7–O0
Output Disable A12 A11 A10 A9A8VIH High Z
Program VILP VPP VILP VILP VIHP VILP D7–D0
Pro gram In hibit VILP VPP VILP VIHP VIHP VILP High Z
Program Verify VILP VPP VILP VIHP VILP VILP O7–O0
Blank Check VILP VPP VILP VIHP VILP VILP O7–O0
Notes:
6. X = “don’t care” but not to exceed VCC ±5%.
7. Addresses A8-A12 must be latched th rough lines A0-A4 in pr ogramming mo des.