Mitsubishi microcomputers
M16C / 62P Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Clock Generation Circuit
72
development
Preliminary Specifications Rev.1.0
Specifications in this manual are tentative and subject to change.
Oscillation Stop and Re-oscillation Detect Function
The oscillation stop and re-oscillation detect function is such that main clock oscillation circuit stop and re-
oscillation are detected. At oscillation stop, re-oscillation detection, reset or oscillation stop, re-oscillation
detection interrupt are generated. Which is to be generated can be selected using the CM27 bit of CM2
register. Table 1.9.4 lists an specification overview of the oscillation stop and re-oscillation detect function.
Table 1.9.7. Specification Overview of Oscillation Stop and Re-oscillation Detect Function
Item
Oscillation stop detectable clock and
f(X
IN
)
≥
2 MHz
frequency bandwidth
Enabling condition for oscillation stop,
Set CM20 bit to “1”(enable)
re-oscillation detection function
Operation at oscillation stop,
Reset occurs (when CM27 bit =0)
re-oscillation detection
Oscillation stop, re-oscillation detection interrupt occurs(when CM27 bit =1)
Specification
(1) Operation When CM27 bit = 0 (Oscillation Stop Detection Reset)
Where main clock stop is detected when the CM20 bit is “1” (oscillation stop, re-oscillation detection
function enabled), the microcomputer is initialized, coming to a halt (oscillation stop reset; refer to “SFR”,
“Reset”).
This status is reset with hardware reset 1 or hardware reset 2. Also, even when re-oscillation is detected,
the microcomputer can be initialized and stopped; it is, however, necessary to avoid such usage. (During
main clock stop, do not set the CM20 bit to “1” and the CM27 bit to “0”.)
(2)
Operation When CM27 bit = 0 (Oscillation Stop and Re-oscillation Detect Interrupt)
Where the main clock corresponds to the CPU clock source and the CM20 bit is “1” (oscillation stop and
re-oscillation detect function enabled), the system is placed in the following state if the main clock comes
to a halt:
Oscillation stop and re-oscillation detect interrupt request occurs.
The ring oscillator starts oscillation, and the ring oscillator clock becomes the CPU clock and clock
source for peripheral functions in place of the main clock.
CM21 bit = 1 (ring oscillator clock for CPU clock source)
CM22 bit = 1 (main clock stop detected)
CM23 bit = 1 (main clock stopped)
Where the PLL clock corresponds to the CPU clock source and the CM20 bit is “1”, the system is placed
in the following state if the main clock comes to a halt: Since the CM21 bit remains unchanged, set it to “1”
(ring oscillator clock) inside the interrupt routine.
Oscillation stop and re-oscillation detect interrupt request occurs.
CM22 bit = 1 (main clock stop detected)
CM23 bit = 1 (main clock stopped)
CM21 bit remains unchanged
Where the CM20 bit is “1”, the system is placed in the following state if the main clock re-oscillates from
the stop condition:
Oscillation stop and re-oscillation detect interrupt request occurs.
CM22 bit = 1 (main clock re-oscillation detected)
CM23 bit = 0 (main clock oscillation)
CM21 bit remains unchanged