Electronics America Computer Hardware User Manual

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 used
to 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 the
format 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
f
CLK/64
fCLK/128
f
CLK/256
fCLK/512
85.3 s
42.7 s
21.3 s
10.7 s
5.3 s
2.6 s
Resolution
f
CLK = 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 f
CLK
: System clock frequency