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S1C88650 TECHNICAL MANUAL EPSON 15
4 INITIAL RESET
4 INITIAL RESET
Initial reset in the S1C88650 is required in order to initialize circuits. This section of the Manual
contains a description of initial reset factors and the initial settings for internal registers, etc.
4.1 Initial Reset Factors
There are two initial reset factors for the S1C88650
as shown below.
(1)
_________
External initial reset by the RESET terminal
(2) External initial reset by the simultaneous LOW
level input at input port terminals K00–K03
(mask option)
Figure 4.1.1 shows the configuration of the initial
reset circuit.
The CPU and peripheral circuits are initialized by
means of initial reset factors. When the factor is
canceled, the CPU commences reset exception
processing. (See the "S1C88 Core CPU Manual".)
When this occurs, the reset exception processing
vector, Bank 0, 000000H–000001H from program
memory is read out and the program (initialization
routine) which begins at the readout address is
executed.
Internal initial
reset
f
OSC3
/1,024 Hz
Reset signal
f
OSC1
/256 Hz
K00
Input port K00
K01
Input port K01
K02
Input port K01
K03
Input port K03
RESET
SLEEP status
Oscillation stability
waiting signal
OSC1
oscillation
circuit
Divider
OSC2
OSC1
OSC3
oscillation
circuit
Divider
Selector
OSC4
OSC3
RQ
S
Operating clock status
Reset release
clock
V
DD
Mask
option
Time
authorize
circuit
Fig. 4.1.1 Configuration of initial reset circuit
____________
4.1.1 RESET terminal
Initial reset can be done by externally inputting a
_________
LOW level to the RESET terminal.
_________
Be sure to maintain the RESET terminal at LOW
level for the regulation time after the power on to
assure the initial reset. (See Section 8.6, "AC
Characteristics".)
_________
In addition, be sure to use the RESET terminal for
the first initial reset after the power is turned on.
_________
The RESET terminal is equipped with a pull-up
resistor. You can select whether or not to use by
mask option.
Input port pull-up resistor
_________
RESET ............■■ With resistor ■■ Gate direct