M16C80 Datasheet, PDF (232/358 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/80 SERIES

M16C/80 Group
27. Usage Precaution
Reducing power consumption
(1) When A/D conversion is not performed, select the Vref not connected with the Vref connect bit of A/D
control register 1. When A/D conversion is performed, start the A/D conversion at least 1 µs or longer
after connecting Vref.
(2) When using AN4 (P104) to AN7 (P107), select the input disable of the key input interrupt signal with
the key input interrupt disable bit of the function select register C .
When selecting the input disable of the key input interrupt signal, the key input interrupt cannot be
used. Also, the port cannot be input even if the direction register of P104 to P107 is set to input (the
input result becomes undefined). When the input disable of the key input interrupt signal is selected,
use all AN4 to AN7 as A/D inputs.
(3) When ANEX0 and ANEX1 are used, select the input peripheral function disable with port P95 and P96
input peripheral function select bit of the function select register B3.
When the input peripheral function disable is selected, the port cannot be input even if the port direc-
tion register is set to input (the input result becomes undefined).
Also, it is not possible to input a peripheral function except ANEX0 and ANEX1.
(4) When D/A converter is not used, set output disabled with the D/A output enable bit of D/A control
register and set the D/A register to "0016".
(5) When D/A conversion is used, select the input peripheral function disabled with port P93 and P94 input
peripheral function select bit of the function select register B3.
When the input peripheral function disabled is selected, the port cannot be input even if the port
direction register is set to input (the input result becomes undefined).
Also, it is not possible to input a peripheral function.
DRAM controller
When shifting to self-refresh, select DRAM ignored by the DRAM space select bit. In the next instruction,
simultaneously set the DRAM space select bit and self-refresh ON by self-refresh mode bit. Also, insert
two NOPs after the instruction that sets the self-refresh mode bit to "1".
Do not access external memory while operating in self-refresh. (All external memory space access is
inhibited. )
When disabling self-refresh, simultaneously select DRAM ignored by the DRAM space select bit and self-
refresh OFF by self-refresh mode bit. In the next instruction, set the DRAM space select bit.
Do not access the DRAM space immediately after setting the DRAM space select bit.
Example) One wait is selected by the wait select bit and 4MB is selected by the DRAM space select bit
Shifting to self-refresh
•••
mov.b
mov.b
nop
nop
•••
#00000001b,DRAMCONT
#10001011b,DRAMCONT
;DRAM ignored, one wait is selected
;Set self-refresh, select 4MB and one wait
;Two nops are needed
;
Disable self-refresh
•••
mov.b #00000001b,DRAMCONT
mov.b
nop
nop
•••
#00001011b,DRAMCONT
;Disable self-refresh, DRAM ignored, one wait is
;selected
;Select 4MB and one wait
;Inhibit instruction to access DRAM area
Rev.1.00 Aug. 02, 2005 ^{Page 221} of 329
REJ09B0187-0100