164
µ
PD78214 Sub-Series
(2) Prescaler mode register 1 (PRM1)The PRM1 register is an 8-bit register used to specify a count clock for 8-bit timer 1 (TM1) and 8-bit timer 2(TM2).The higher 4 bits are used to specify a count clock for TM2 of 8-bit timer/counter 2. (The lower 4 bits are usedto specify a count clock for TM1 of 8-bit timer/counter 1.)The PRM1 register allows only write operation using an 8-bit manipulation instruction. Fig. 7-68 shows theformat of the PRM1 register.When the RESET signal is applied, the PRM1 register is cleared to 00H.Fig. 7-68 Format of Prescaler Mode Register 1 (PRM1)
PRS23
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 1 1 1
Specification of count clock [Hz]
fCLK/16
fCLK/32
fCLK/64
fCLK/128
fCLK/256
fCLK/512 85.3 s
42.7 s
21.3 s
10.7 s
5.3 s
2.6 s
Resolution
fCLK = 6 MHz
These bits specify the count clock supplied to
8-bit timer/counter 1 (TM1) (see Fig. 7-45).
76543210
PRM1 PRS23 0
PRS22 PRS21 PRS20 PRS12 PRS11 PRS10
PRS22 PRS21 PRS20
External clock (CI)
µ
µ
µ
µ
µ
µ
Remark fCLK: System clock frequency