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| AT89S8253_08 Datasheet, PDF (6/59 Pages) ATMEL Corporation – 8-bit Microcontroller with 12K Bytes Flash and 2K Bytes EEPROM | |||
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3.13 EA/VPP
3.14 XTAL1
3.15 XTAL2
External Access Enable. EA must be strapped to GND in order to enable the device to fetch
code from external program memory locations starting at 0000H up to FFFFH. Note, however,
that if lock bit 1 is programmed, EA will be internally latched on reset.
EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt
programming enable voltage (VPP) during Flash programming when 12-volt programming is
selected.
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
Output from the inverting oscillator amplifier.
4. Block Diagram
VCC
GND
P0.0 - P0.7
PORT 0 DRIVERS
P2.0 - P2.7
PORT 2 DRIVERS
EEPROM
RAM ADDR.
REGISTER
RAM
PORT 0
LATCH
PORT 2
LATCH
FLASH
PSEN
ALE/PROG
EA / VPP
RST
B
REGISTER
ACC
STACK
POINTER
PROGRAM
ADDRESS
REGISTER
TMP2
TMP1
ALU
PSW
INTERRUPT, SERIAL PORT,
AND TIMER BLOCKS
TIMING
AND
CONTROL
INSTRUCTION
REGISTER
WATCH
DOG
PORT 3
LATCH
PORT 1
LATCH
SPI
PORT
BUFFER
PC
INCREMENTER
PROGRAM
COUNTER
DUAL
DPTR
PROGRAM
LOGIC
OSC
PORT 3 DRIVERS
PORT 1 DRIVERS
P3.0 - P3.7
P1.0 - P1.7
6 AT89S8253
3286LâMICROâ8/08
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