27C256-30I Просмотр технического описания (PDF) - Microchip Technology
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27C256-30I Datasheet PDF : 10 Pages
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27LV256
1.3 Standby Mode
The standby mode is defined when the CE pin is high
(VIH) and a program mode is not defined. Output Dis-
able
1.4 Output Enable
This feature eliminates bus contention in multiple bus
microprocessor systems and the outputs go to a high
impedance when the following condition is true:
• The OE pin is high and program mode is not
defined.
1.5 Programming Mode
The Express algorithm has been developed to improve
on the programming throughput times in a production
environment. Up to 10 100-microsecond pulses are
applied until the byte is verified. No over-programming
is required. A flowchart of the express algorithm is
shown in Figure 1.
Programming takes place when:
a) VCC is brought to the proper voltage
b) VPP is brought to the proper VH level
c) the OE pin is high
d) the CE pin is low
Since the erased state is “1” in the array, programming
of “0” is required. The address to be programmed is set
via pins A0-A14 and the data to be programmed is pre-
sented to pins O0-O7. When data and address are sta-
ble, a low-going pulse on the CE line programs that
location.
1.6 Verify
After the array has been programmed it must be veri-
fied to ensure that all the bits have been correctly pro-
grammed. This mode is entered when all of the
following conditions are met:
a) VCC is at the proper level
b) VPP is at the proper VH level
c) the CE pin is high
d) the OE line is low
1.7 Inhibit
When Programming multiple devices in parallel with
different data, only CE needs to be under separate con-
trol to each device. By pulsing the CE line low on a par-
ticular device, that device will be programmed, and all
other devices with CE held high will not be pro-
grammed with the data although address and data are
available on their input pins.
1.8 Identity Mode
In this mode specific data is outputted which identifies
the manufacturer as Microchip Technology Inc. and
device type. This mode is entered when Pin A9 is
taken to VH (11.5V to 12.5V). The CE and OE lines
must be at VIL. A0 is used to access any of the two
non-erasable bytes whose data appears on O0 through
O7.
Pin
Input
Output
Identity
A0 0 O O O O O O O H
76543210 e
x
Manufacturer VIL 0 0 1 0 1 0 0 1 29
Device Type* VIH 1 0 0 0 1 1 0 0 8C
* Code subject to change.
DS11020H-page 6
2004 Microchip Technology Inc.
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