AT90S8515

Manufacturer Part NumberAT90S8515
Description8-bit microcontroller with 8K bytes in-system programmable flash, 2.7-6.0V
ManufacturerATMEL Corporation
AT90S8515 datasheet
 
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Page 23/112:

Reset Sources

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Reset Sources

0841G–09/01
$00f
ldi r16,low(RAMEND)
$010
out SPL,r16
$011
<instr>
The AT90S8515 has three sources of reset:
Power-on Reset. The MCU is reset when the supply voltage is below the Power-on
Reset threshold (V
).
POT
External Reset. The MCU is reset when a low level is present on the RESET pin for
more than 50 ns.
Watchdog Reset. The MCU is reset when the Watchdog timer period expires and
the Watchdog is enabled.
During reset, all I/O registers are set to their initial values and the program starts execu-
tion from address $000. The instruction placed in address $000 must be an RJMP
(relative jump) instruction to the reset handling routine. If the program never enables an
interrupt source, the interrupt vectors are not used and regular program code can be
placed at these locations. The circuit diagram in Figure 23 shows the reset logic. Table 3
defines the timing and electrical parameters of the reset circuitry.
Figure 23. Reset Logic
Table 3. Reset Characteristics
Symbol
Parameter
Power-on Reset Threshold Voltage (rising)
(Not
V
POT
e:)
Power-on Reset Threshold Voltage (falling)
V
RESET Pin Threshold Voltage
RST
Reset Delay Time-out Period FSTRT
t
TOUT
Unprogrammed
Reset Delay Time-out Period FSTRT
t
TOUT
Programmed
Note:
The Power-on Reset will not work unless the supply voltage has been below V
(falling).
AT90S8515
xxx
Min
Typ
0.8
1.2
0.2
0.4
11.0
16.0
0.25
0.28
Max
Units
1.6
V
0.6
V
0.9 V
V
CC
21.0
ms
0.31
ms
POT
23