deveopmen
BCLK Status
Preliminary Specifications REV.D
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M16C/80 (100-pin version) group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
48
Status Transition of BCLK
Power dissipation can be reduced and low-voltage operation achieved by changing the count source for
BCLK. Table 1.8.6 shows the operating modes corresponding to the settings of system clock control
registers 0 and main clock division register.
After a reset, operation defaults to division by 8 mode. When shifting to stop mode, reset or stopping main
clock, the main clock division register (address 000C
16
) is set to “08
16
”.
(1) Division by 2 mode
The main clock is divided by 2 to obtain the BCLK.
(2) Division by 3 mode
The main clock is divided by 3 to obtain the BCLK.
(3) Division by 4 mode
The main clock is divided by 4 to obtain the BCLK.
(4) Division by 6 mode
The main clock is divided by 6 to obtain the BCLK.
(5) Division by 8 mode
The main clock is divided by 8 to obtain the BCLK. After reset, this mode is executed. Note that oscillation
of the main clock must have stabilized before transferring from this mode to no-division, division by 2, 6,
10, 12, 14 and 16 mode.
Oscillation of the sub clock must have stabilized before transferring to low-speed and low power dissipa-
tion mode.
(6) Division by 10 mode
The main clock is divided by 10 to obtain the BCLK.
(7) Division by 12 mode
The main clock is divided by 12 to obtain the BCLK.
(8) Division by 14 mode
The main clock is divided by 14 to obtain the BCLK.
(9) Division by 16 mode
The main clock is divided by 16 to obtain the BCLK.
(10) No-division mode
The main clock is divided by 1 to obtain the BCLK.
(11) Low-speed mode
f
C
is used as BCLK. Note that oscillation of both the main and sub clocks must have stabilized before
transferring from this mode to another or vice versa. At least 2 to 3 seconds are required after the sub
clock starts. Therefore, the program must be written to wait until this clock has stabilized immediately
after powering up and after stop mode is cancelled.
(12) Low power dissipation mode
f
C
is the BCLK and the main clock is stopped.
When the main clock is stoped, the main clock division register (address 000C
16
) is set to the division by
8 mode.