deveopmen
Wait Mode
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
47
Table 1.8.5. Port status during wait mode
Pin
Memory expansion mode
Microprocessor mode
Single-chip mode
________
RD, WR, WRL, WRH, DW, CASL,
CASH
________
__________
ALE
Port
CLK
OUT
When f
C
selected
When f
8
, f
32
selected Does not stop when the WAIT peripheral function clock stop bit
is “0”. When the WAIT peripheral function clock stop bit is “1”,
the status immediately prior to entering wait mode is main-
tained.
Note :When self-refresh is done in operating DRAM control, CAS and RAS becomes “L”.
Retains status before wait mode
“H” (Note)
“H” (Note)
“H”
“L”
Retains status before wait mode
Does not stop
Retains status before wait mode
Wait Mode
When a WAIT instruction is executed, the BCLK stops and the microcomputer enters the wait mode. In this
mode, oscillation continues but the BCLK and watchdog timer stop. Writing “1” to the WAIT peripheral
function clock stop bit and executing a WAIT instruction stops the clock being supplied to the internal
peripheral functions, allowing power dissipation to be reduced. Table 1.8.5 shows the status of the ports in
wait mode.
Wait mode is cancelled by a hardware reset or interrupt. If an interrupt is used to cancel wait mode, the
microcomputer restarts using as BCLK the clock that had been selected when the WAIT instruction was
executed.
When using an interrupt to exit Wait mode, the relevant interrupt must have been enabled and set to a
priority level above the level set by the interrupt priority set bits for exiting a stop/wait state (bits 2, 1, and 0
at address 009F
16
). Set the interrupt priority set bits for the exit from a stop/wait state to the same level as
the flag register (FLG) processor interrupt level (IPL).
When using an interrupt to exit Wait mode, the microcomputer resumes operating the clock that was oper-
ating when the WAIT command was executed as BCLK from the interrupt routine.