AT89S8253 Atmel Corporation, AT89S8253 Datasheet - Page 11
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AT89S8253
Manufacturer Part Number
AT89S8253
Description
Manufacturer
Atmel Corporation
Datasheets
1.AT89S8253.pdf
(60 pages)
2.AT89S8253.pdf
(2 pages)
3.AT89S8253.pdf
(2 pages)
4.AT89S8253.pdf
(2 pages)
Specifications of AT89S8253
Flash (kbytes)
12 Kbytes
Max. Operating Frequency
24 MHz
Cpu
8051-12C
Max I/o Pins
32
Spi
1
Uart
1
Sram (kbytes)
0.25
Eeprom (bytes)
2048
Operating Voltage (vcc)
2.7 to 5.5
Timers
3
Isp
SPI
Watchdog
Yes
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7. Power-On Reset
Figure 7-1.
7.1
3286P–MICRO–3/10
Min V
Memory Brown-out Protection
BOD Level 2.3V
POR Level 1.4V
CC
WRTINH
Level 2.7V
Internal
RESET
XTAL1
Power-up and Brown-out Detection Sequence
POR
V
0
CC
A Power-On Reset (POR) is generated by an on-chip detection circuit. The detection level is
nominally 1.4V. The POR is activated whenever V
cuit can be used to trigger the start-up reset or to detect a supply voltage failure in devices
without a brown-out detector. The POR circuit ensures that the device is reset from power-on.
When V
how long the device is kept in POR after V
again, without any delay, when V
a cold reset) will set the POF flag in PCON.
The AT89S8253 has an on-chip Brown-out Detection (BOD) circuit for monitoring the V
during operation by comparing it to a fixed trigger level of nominally 2.2V (2.4V max). The pur-
pose of the BOD is to ensure that if V
erased/written at voltages too low for programming. At powerup the V
BOD threshold before execution starts. When V
the WRTINH bit in EECON is activated and futher programming of the Flash/EEPROM is
restricted. When V
ming until after the timeout period has expired in approximately 2 ms. The BOD does not reset
the system as shown in
cution at lower voltages an external BOD circuit may be required.
(2 ms)
t
POR
CC
reaches the Power-on Reset threshold voltage, the POR delay counter determines
2.4V
CC
increases above the trigger level, the BOD delay counter blocks program-
Figure
7-1. To protect the system from errors induced by incorrect exe-
CC
falls below the POR threshold level. A Power-On Reset (i.e.
CC
fails or dips, the Flash or EEPROM memories cannot be
1.2V
CC
rise, nominally 2 ms. The POR signal is activated
CC
CC
decreases to a value below the trigger level,
is below the detection level. The POR cir-
(2 ms)
CC
t
POR
AT89S8253
level must pass the
t
t
t
t
t
CC
level
11