CY27C128
4
Switching Waveform
tOH
tPU
tPD
tAA
C1286
(tOE)
tACE
50%
50%
A0 - A13
ADDRESS
ICC
SUPPLY
CURRENT
OE, CE
O0 - O7 PREVIOUS DATA VALID
DATA VALID
POWERDOWN CONTROLLED BY CE
(tHZOE)
tHZCE
HIGH Z
Erasure Characteristics
Wavelengths of light less than 4000 Å begin to erase the 27C128
in the windowed package. For this reason, an opaque label should
be placed over the window if the EPROM is exposed to sunlight
or fluorescent lighting for extended periods of time.
The recommended dose of ultraviolet light for erasure is a wave
length of 2537 Å for a minimum dose (UV intensity multiplied by
exposure time) of 25 Wsec/cm2. For an ultraviolet lamp with a 12
mW/cm2 power rating, the exposure time would be approximately
35 minutes. The CY27C128 needs to be within 1 inch of the lamp
during erasure. Permanent damage may result if the EPROM is
exposed to highintensity UV light for an extended period of
time. 7258 Wsec/cm2 is the recommended maximum dosage.
Programming Modes
Programming support is available from Cypress as well as from a
number of thirdparty software vendors. For detailed program
ming information, including a listing of software packages, please
see the EPROM Programming Information located at the end of
this section. Programming algorithms can be obtained from any
Cypress representative.
Table 1. CY27C128 Mode Selection
Pin Function[9]
Mode
A13 - A0
OE
CE
VPP
PGM
O7 - O0
Read
A13 - A0
VIL
VIL
X
Note 10
O7 - O0
Output Disable
A13 - A0
VIH
X
X
Note 10
High Z
Power Down
A13 - A0
X
VIH
X
Note 10
High Z
Notes:
9. X must be either VIL or VIH.
10. X must be either VIL or VIH (must not switch).
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