CY7C265
Switching Waveform
ADDRESS
t
AS
t
SYNCHRONOUS
ENABLE
(PROGRAMMABLE)
AH
t
HES
t
SES
CLOCK
t
t
t
CO
PWC
COS
VALID DATA
OUTPUT
t
DOE
t
DI
t
HZC
t
HZE
t
PWI
ASYNCHRONOUS INIT
(PROGRAMMABLE)
t
RI
ASYNCHRONOUS
ENABLE
Control Byte
Erasure Characteristics
00 Asynchronous output enable (default condition)
01 Synchronous output enable
02 Asynchronous initialize
Wavelengths of light less than 4000 angstroms begin to erase
the 7C265 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.
Programming Modes
The 7C265 offers a limited selection of programmed architec-
tures. Programming these features should be done with a sin-
gle 10-ms-wide pulse in place of the intelligent algorithm,
mainly because these features are verified operationally, not
with the VFY pin. Architecture programming is implemented by
applying the supervoltage to two additional pins during pro-
gramming. In programming the 7C265 architecture, VPP is ap-
plied to pins 3, 9, and 22. The choice of a particular mode
depends on the states of the other pins during programming,
so it is important that the condition of the other pins be met as
set forth in the mode table. The considerations that apply with
respect to power-up and power-down during intelligent pro-
gramming also apply during architecture programming. Once
the supervoltages have been established and the correct logic
states exist on the other device pins, programming may begin.
Programming is accomplished by pulling PGM from HIGH to
LOW and then back to HIGH with a pulse width equal to 10 ms.
The recommended dose of ultraviolet light for erasure is a
wavelength of 2537 angstroms for a minimum dose (UV inten-
sity • exposure time) of 25 Wsec/cm2. For an ultraviolet lamp
with a 12 mW/cm2 power rating the exposure time would be
approximately 45 minutes. The 7C265 needs to be within one
inch of the lamp during erasure. Permanent damage may re-
sult if the PROM is exposed to high-intensity UV light for an
extended period of time. 7258 Wsec/cm2 is the recommended
maximum dosage.
Bit Map Data
Programmer Address (Hex.)
RAM Data
Contents
Decimal
Hex
0
.
.
0
.
.
Data
.
.
8191
8192
8193
1FFF
2000
2001
Data
INIT Byte
Control Byte
Document #: 38-04012 Rev. **
Page 5 of 13
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