GMS81508B HYNIX [Hynix Semiconductor], GMS81508B Datasheet - Page 73

• Manufacturer Part Number: GMS81508B
• Description: HYUNDAI MICRO ELECTRONICS 8-BIT SINGLE-CHIP MICROCONTROLLERS
• Manufacturer: HYNIX [Hynix Semiconductor]

GMS81508B/16B/24B
20. RESET
The GMS815xxB have two types of reset generation pro-
cedures; one is an external reset input, the other is a watch-
20.1 External Reset Input
The reset input is the RESET pin, which is the input to a
Schmitt Trigger. A reset in accomplished by holding the
RESET pin low for at least 8 oscillator periods, within the
operating voltage range and oscillation stable, it is applied,
and the internal state is initialized. After reset, 64ms (at 4
MHz) add with 7 oscillator periods are required to start ex-
ecution as shown in Figure 20-2.
Internal RAM is not affected by reset. When V
on, the RAM content is indeterminate. Therefore, this
RAM should be initialized before read or tested it.
When the RESET pin input goes to high, the reset opera-
tion is released and the program execution starts at the vec-
tor address stored at addresses FFFE
20.2 Watchdog Timer Reset
Refer to “17. WATCHDOG TIMER” on page 64.
70
Program counter
G-flag
Peripheral clock
On-chip Hardware
ADDRESS
Oscillator
(X
RESET
BUS
DATA
IN
BUS
pin)
(PC)
(G)
Table 20-1 Initializing Internal Status by Reset Action
(FFFF
H
Initial Value
- FFFF
Figure 20-2 Timing Diagram after RESET
?
?
H
) - (FFFE
Off
0
H
DD
.
t
ST
Stabilization Time
is turned
= 62.5mS at 4.19MHz
H
)
Watchdog timer
Control registers
Power fail detector
1
On-chip Hardware
dog timer reset. Table 20-1 shows on-chip hardware ini-
tialization by reset action.
A connection for simple power-on-reset is shown in Figure
20-1.
?
2
t
ST
RESET Process Step
Figure 20-1 Simple Power-on-Reset Circuit
?
=
3
?
f
MAIN
?
4
1
1024
?
V
7036P
?
CC
5
x 256
FE
FFFE FFFF
6
HYUNDAI MicroElectronics
ADL
Refer to Table 8-1 on page 25
7
+
10k
10uF
ADH
Start
DEC. 1999 Ver 1.04
OP
Initial Value
to the RESET pin
MAIN PROGRAM
Disable
Disable