TMP92C820FG Datasheet, PDF (24/382 Pages) Toshiba Semiconductor – Original CMOS 16-Bit Microcontroller

TMP92C820
(2) Clock gear controller
f_FPH is set according to the contents of the clock gear select register
SYSCR1<GEAR2:0> to either fc, fc/2, fc/4, fc/8 or fc/16. Using the clock gear to select a
lower value of f_FPH reduces power consumption.
Example 3:
Changing to a high-frequency gear
SYSCR1 EQU
LD
X: Don’t care
10E1H
(SYSCR1), XXXX0000B ; Changes f_SYS to fc/2.
(High-speed clock gear changing)
To change the clock gear, write the register value to the SYSCR1<GEAR2:0> register. It
is necessary the warm-up time until changing after writing the register value.
There is the possibility that the instruction next to the clock gear changing instruction is
executed by the clock gear before changing. To execute the instruction next to the clock gear
switching instruction by the clock gear after changing, input the dummy instruction as
follows (Instruction to execute the write cycle).
(Example)
SYSCR1
EQU
LD
LD
10E1H
(SYSCR1), XXXX0001B ;
(DUMMY), 00H
;
Instruction to be executed
after clock gear has changed
Changes f_SYS to fc/4.
Dummy instruction
92C820-22
2007-02-16