TMP91C824
91C824-21
(2) Clock gear controller
When the high-frequency clock fc is selected by setting SYSCR1<SYSCK> = 0, f
FPH
is set
according to the contents of the Clock Gear Select Register SYSCR1<GEAR0 to GEAR2> 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
00E1H
LD
(SYSCR1), XXXX0000B
;
Changes f
SYS
to fc/2.
LD
(SYSCR1), XXXX0100B
;
Changes f
SYS
to fc/32.
X: Don't care
(High-speed clock gear changing)
To change the clock gear, write the register value to the SYSCR1<GEAR2-0> register.It is necessary the
warmming 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
00E1H
LD
(SYSCR1), XXXX0001B
;
Changes f
SYS
to fc/4.
LD
(DUMMY), 00H
;
Dummy instruction
Instruction to be executed after clock gear has changed
(3) Internal clock terminal out function
It can out internal clock(f
SYS
or f
S
) from PD5/SCOUT.
PD5 pin function is set to SCOUT output by the following bit setting.
: PDFC<PD5F>=’1’
Output clock select
:Refer to SYSCR2<SCOSEL> bit setting
HALT mode
HALT mode
SCOUT select
NORMAL
SLOW
IDLE2
IDEL1
STOP
<SCOSEL>=’0’
f
S
clock out
<SCOSEL>=’1’
f
SYS
clock out
‘0’ or ‘1’ fix out