User’s Manual U12688EJ4V0UM00
409
CHAPTER 13 RESET FUNCTIONS
When a low-level signal is input to the RESET pin, a system reset is effected and the hardware is initialized.
When the RESET signal level changes from low to high, the reset state is released and program execution is
started. Register contents must be initialized as required in the program.
13.1 Features
The reset pin (RESET) incorporates a noise eliminator which uses analog delay (
≅
60 ns) to prevent malfunction
due to noise.
13.2 Pin Functions
During a system reset, most pins (all but the CLKOUT
Note
, RESET, X2, HV
DD
, V
DD
, V
SS
, CV
DD
, CV
SS
, AV
DD
, AV
SS
,
and AV
REF
pins) enter the high impedance state. Therefore, when memory is connected externally, a pull-up or pull-
down resistor must be connected to the specified pins of ports 4, 5, 6, 8, 9, A, B, and X. If no resister is connected
there, memory contents may be lost when these pins enter high impedance state. For the same reason, the output
pins of the internal peripheral I/O functions and output ports should be handled in the same manner.
Note In ROM-less modes 0 and 1, and in single-chip mode 1, the CLKOUT signal is output even during reset. In
single-chip mode 0, the CLKOUT signal is not output until the PMCX register is set.
Table 13-1 shows the operating state of each output pin and each input/output pin during reset.
Table 13-1. Operating State of Each Pin During Reset
Pin State
Pin Name
When in Single-
Chip Mode 0
When in Single-
Chip Mode 1
When in ROM-
less Mode 0
When in ROM-
less Mode 1
D0 to D7, A0 to A23, CS0 to CS7, RAS0
to RAS7, LCAS, LWR, UCAS, UWR, RD,
WE, BCYST, OE, HLDAK, REFRQ
(Port mode)
High-impedance
D8 to D15
(Port mode)
High-impedance
(Port mode)
WAIT, HLDRQ
(Port mode)
(Input)
CLKOUT
(Port mode)
Operating
Ports 0 to 3, 10 to 12
(Input)
Ports 4, 6, 8, 9, A, B, X
(Input)
(Control mode)
Port pin
Port 5
(Input)
(Control mode)
(Input)
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