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User’s Manual U14492EJ3V0UD
CHAPTER 15 RESET FUNCTION
When a low level is input to the RESET pin, there is a system reset and each hardware item of the V850E/IA1 is
initialized to its initial status.
When the RESET pin changes from low level to high level, reset status is released and the CPU starts program
execution. Initialize the contents of various registers as needed within the program.
15.1 Features
• Noise elimination using analog delay (approx. 60 ns) in reset pin (RESET)
15.2 Pin Functions
During a system reset period, most pin output is high impedance (all pins except CLKOUT
Note
, RESET, X2, V
DD5
,
V
SS5
, V
DD3
, V
SS3
, CV
DD
, CV
SS
, AV
DD
, AV
REF0
, AV
REF1
, and AV
SS
pins).
Thus, if for example memory is extended externally, a pull-up (or pull-down) resistor must be attached to each pin
of ports DH, DL, CS, CT, and CM. If there are no resistors, the external memory that is connected may be destroyed
when these pins become high impedance.
Similarly, perform pin processing so that on-chip peripheral I/O function signal output and output ports are not
affected.
Note
In ROMless mode 0 or 1 and single-chip mode 1, CLKOUT signals also are output during a reset period.
In single-chip mode 0, CLKOUT signals are not output until the PMCCM register is set.
Table 15-1 shows the operation status of each pin during a reset period.
Table 15-1. Operation Status of Each Pin During Reset Period
Pin Status
Pin Name
In Single-Chip
Mode 0
In Single-Chip
Mode 1
In ROMless
Mode 0
In ROMless
Mode 1
A16 to A23, AD0 to AD15, CS0 to CS7,
LWR, UWR, RD, ASTB, WAIT, HLDAK,
HLDRQ
(Port mode)
High impedance
CLKOUT
(Port mode)
Operation
Ports 0 to 4
(Input)
Port pins
Ports CM, CS, CT, DH, DL
(Input)
(Control mode)
Содержание V850E/IA1 mPD703116
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