deveopmen
Watchdog Timer
Preliminary Specifications REV.B
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M16C/80 (144-pin version) group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
76
Watchdog timer control register
Symbol
WDC
Address
000F
16
When reset
000XXXXX
2
Function
Bit symbol
b7
b6
0
b5
0
b4
b3
b2
b1
b0
High-order bit of watchdog timer
WDC7
Bit name
Prescaler select bit
0 : Divided by 16
1 : Divided by 128
Watchdog timer start register
Symbol
WDTS
Address
000E
16
When reset
Indeterminate
W
R
b7
b0
Function
The watchdog timer is initialized and starts counting after a write instruction to
this register. The watchdog timer value is always initialized to “7FFF
16
”
regardless of whatever value is written.
Reserved bit
Must always be set to “0”
AA
AA
AA
AA
A
Figure 1.10.2. Watchdog timer control and start registers
System clock control register 0 (Note 1)
Symbol
CM0
Address
0006
16
When reset
08
16
Bit
Function
Bit symbol
b7
b6
b5
b4
b3 b2
b1
b0
3
0 1 : f
C
output (Note 3)
1 0 : f
8
output (Note 3)
1 1 : f
32
output (Note 3)
0 : Do not stop f
1
, f
8
, f
32
in wait mode
1 : Stop f
1
, f
8
, f
32
in wait mode
0 : LOW
1 : HIGH
b1 b0
CM07
CM05
CM04
CM03
CM01
CM02
CM00
Clock outpname
select bit (Note 2)
WAIT peripheral function
clock stop bit
X
CIN
-X
COUT
drive capacity
select bit (Note 4)
Port X
C
select bit
0 : I/O port
1 : X
CIN
-X
COUT
generation
0 : On
1 : Off (Note 7)
0 : Watchdog timer interrupt
1 : Reset (Note 8)
Main clock (X
IN
-X
OUT
)
stop bit (Note 5, 6)
Watchdog timer function
select bit
System clock select bit
(Note 9)
0 : X
IN
, X
OUT
1 : X
CIN
, X
COUT
Note 1: Set bit 0 of the protect register (address 000A
16
) to “1” before writing to this register.
Note 2: When outputting BCLK (bit 7 of processor mode register 0 is "0"), set these bits to "00". When
outputting ALE to P5
3
(bit 5 and 4 of processor mode register 0 is "01"), set these bits to "00". The
port P5
3
function is not selected even when you set "00" in microprocessor or memory expansion
mode and bit 7 of the processor mode register 0 is "1".
Note 3: When selecting f
C
, f
8
or f
32
in single chip mode, must use P5
7
as input port.
Note 4: Changes to “1” when shifting to stop mode or reset.
Note 5: When entering power saving mode, main clock stops using this bit. When returning from stop
mode and operating with X
IN
, set this bit to “0”.
Note 6: When this bit is "1", X
OUT
is "H". Also, the internal feedback resistance remains ON, so X
IN
is pulled
up to X
OUT
("H" level) via the feedback resistance.
Note 7: When the main clock is stopped, the main clock division register (address 000C
16
) is set to the
division by 8 mode.
Note 8: When "1" has been set once, "0" cannot be written by software.
Note 9: To set CM07 "1" from "0", first set CM04 to "1", and an oscillation of sub clock is stable. Then set
CM07. Do not set CM04 and CM07 simultaneously. Also, to set CM07 "0" from "1", first set CM05
to "1", and an oscillation of main clock is stable. Then set CM07.
AA
AA
AA
AA
AA
AA
AA
AA
AA
CM06