CY7C261
CY7C263/CY7C264
Document #: 38-04010 Rev. *B Page 5 of 14
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
periods of time.
The recommended dose of ultraviolet light for erasure is a
wavelength of 2537 angstroms for a minimum dose (UV
intensity multiplied by exposure time) of 25 Wsec/cm2. For an
ultraviole t lamp with a 12 mW/cm 2 power rating, the ex posure ti me
would be approximately 35 minutes. The 7C261 or 7C263
needs to be within 1 inch of the lamp during erasure.
Permanent damage 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 fo r 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 the contents of the addressed location
appear on the data out pins.
Program, Program Inhibit, Program Verify
These m odes are en tered b y pla cing a high volt age VPP on pin
19, with pin s 18 and 20 set t o V ILP. In this state, pin 21 becomes a
latch signal, allo wi ng the upp er 5 addr ess bits to b e latc hed into an
onboard r egister, pin 22 be comes an act ive LOW progr am (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
PROGRAM mode exists when PGM is LOW, and VFY is HIGH. The
verify mode exists wh en the reverse is tru e, PGM HIGH and VFY
LOW and the prog ram inhib it mode is ente red wi th 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 in g Waveform s[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 Inhibit 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 throug h lines A0-A4 in programmin g modes.