CY7C261

CY7C263/CY7C264

Document #: 38-04010 Rev. **

Page 5 of 16

Erasure Characteristics

Wavelengths of light less than 4000 angstroms begin 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

wavelength of 2537 angstroms for a minimum dose (UV inten-

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

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 the contents of the addressed location

appear on the data out pins.

Program, Program Inhibit, Program Verify

latch signal, allowing the upper 5 address bits to be latched into an

onboard register, pin 22 becomes an active LOW program (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

Switching Waveforms[4]

SUPPLY

CURRENT

ADDRESS

CS

50%

50%

Table 1. Mode Selection

Pin Function[6, 7]

Read or Output Disable

CS

Mode

Program

NA

LATCH

PGM

VFY

CS

Read

Output Disable

High Z

Program

Program Inhibit

High Z

Program Verify

Blank Check

Notes:

6.

7.