4570 Datasheet, PDF (36/69 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
4570 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER
LIST OF PRECAUTIONS
ΠNoise and latch-up prevention
Connect a capacitor on the following condition to prevent noise
and latch-up;
• connect a capacitor (approx. 0.1 µF) between pins VDD and
VSS at the shortest distance,
• equalize its wiring in width and length, and
• use the thickest wire.
In the One Time PROM version, CNVSS pin is also used as
VPP pin. Accordingly, when using this pin, connect this pin to
VSS through a resistor about 5 kΩ (connect this resistor to
CNVSS/VPP pin as close as possible).
 Prescaler
Stop the prescaler operation to change its frequency dividing
ratio.
Ž Count source
Stop timer 1, timer 2 or timer 3 counting to change its count
source.
 Reading the timer count value
Stop each of the timers and then execute the TAB1, TAB2 or
TAB3 instruction to read timer 1, 2 or 3 data.
 Writing to reload register R1
When writing the data to reload register R1 while timer 1 is
operating, avoid a timing when timer 1 underflows.
‘ Writing to reload register R3H
When writing the data to reload register R3H while timer 3 is
operating, avoid a timing when timer 3 underflows.
’ Notes on timer 3 operation start
Set the timer 1 and register C2 before timer 3 is started to
operate (W33=“1”).
“ Notes on carrier wave output auto-control operation stop
Stop the timer 1 (W10=“0”) after stopping the timer 3 (W33=“0”)
while the carrier wave output is disabled in order to stop the
carrier wave output auto-control operation.
” Notes on setting carrier wave output control regiter C2
If the carrier wave output auto-control function is invalidated
(C20=“0”) while the carrier wave output is auto-controlled, the
output of port CARR retains the state when the auto-control is
invalidated regardless of timer 1 underflow.
When the carrier wave output auto-control function is validated
(C20=“1”) again after it is invalidated (C20=“0”), the auto-control
by timer 1 is validated again when the next timer 1 underflow
occurs.
However, when the carrier wave output auto-control bit (C20)
is changed during timer 1 underflow, the error-operation may
occur.
• Notes on timer 1 count source
When the carrier wave output auto-control function is selected,
use the carrier wave CARRY as the timer 1 count source.
If the ORCLK is used as the count source, a short pulse may
occur in port CARR output because ORCLK is not
synchronized with the carrier wave.
11 _{Notes on writing to reload register R1 when carrier wave output}
auto-control operation
When the carrier wave output auto-control function is selected
and data is set to reload register R1 while timer 1 is operating,
avoid the timing that the contents of timer 1 becomes “0” to
execute the T1AB instruction.
12 _{One Time PROM version}
The operating power voltage of the One Time PROM version
is within the range of 2.5 V to 5.5 V.
13 _{Multifunction}
Note that the port D9 output function and P21 input function
can be used even when TOUT and INT pin function is selected.
14 _{POF instruction}
Note that system cannot enter the RAM back-up state when
executing only the POF instruction.
Execute the POF instruction immediately after executing the
EPOF instruction to enter the RAM back-up.
Be sure to disable interrupts by executing the DI instruction
before executing the EPOF instruction.
15 _{Program counter}
Make sure that the PCH does not specify after the last page of
the built-in ROM.
16 _{P21/INT pin}
When the interrupt valid waveform of P21/INT pin is changed
with the bit 2 of register I1 in software, be careful about the
following notes.
• Clear the bit 0 of register V1 to “0” and then change the
interrupt valid waveform of P21/INT pin with the bit 2 of
register I1 (refer to Figure 34Œ).
• Clear the bit 2 of register I1 to “0” and execute the SNZ0
instruction to clear the EXF0 flag after executing at least
one instruction (refer to Figure 34). Depending on the input
state of the P21/INT pin, the external 0 interrupt request flag
(EXF0) may be set to “1” when the interrupt valid waveform
is changed.
._..
LA 4
TV1A
; (!!!02)
; The SNZ0 instruction is valid Œ
LA
TI1A
NOP
SNZ0
NOP
._..
4
; Change of the interrupt valid waveform

;The SNZ0 instruction is executed
! : this bit is not related to the setting of INT.
Fig. 34 External 0 interrupt program example
35