10
10-12
MULTIJUNCTION TIMERS
10.2 Common Units of Multijunction Timers
32180 Group User’s Manual (Rev.1.0)
10.2.2 Prescaler Unit
The Prescalers PRS0–5 area an 8-bit counter, which generates clocks supplied to each timer (TOP, TIO, TMS,
TML, TID and TOU) from the internal peripheral clock (BCLK) divided by 2 (10 MHz when f(BCLK) = 20 MHz).
The values of prescaler registers are initialized to H’00 immediately after reset. When the set value of any
prescaler register is rewritten, the prescaler starts operating with the new value at the same time it has
underflowed.
Values H’00 to H’FF can be set in the prescaler register. The prescaler’s divide-by ratio is given by the equation
below:
Prescaler divide-by ratio =
1
prescaler set value + 1
Prescaler Register 0 (PRS0)
<Address: H
’0080 0202>Prescaler Register 1 (PRS1)
<Address: H
’0080 0203>Prescaler Register 2 (PRS2)
<Address: H
’0080 0204>Prescaler Register 3 (PRS3)
<Address: H
’0080 07D0>Prescaler Register 4 (PRS4)
<Address: H
’0080 0BD0>Prescaler Register 5 (PRS5)
<Address: H
’0080 0CD0>9 1011121314b15b8
123456b7b0
PRS0–PRS5
00000000
<After reset: H’00>
b Bit Name Function R W
0–7 PRS0–PRS5 Set the prescaler divide-by value R W
(8–15) Prescaler
Prescaler Registers 0–2 start counting immediately after reset. Prescaler Registers 3–5 each are activated by
setting the TID0 Control & Prescaler 3 Enable Register, TID1 Control & Prescaler 4 Enable Register or TID2
Control & Prescaler 5 Enable Register’s prescaler-n enable (PRSnEN) bit to "1" (count start), upon which the
prescaler register value is reloaded and the prescaler starts counting. For details, see Section 10.7, “TID (Input-
Related 16-Bit Timer).”
If the prescaler register is accessed for read during operation, the value written into it, not the current count, is
read out.
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