NEC PD78214 - Manual (Page 236)

207
Chapter 7 Timer/Counter Units
7
7.4.3 8-Bit Timer/Counter 3 Control Registers
(1) Timer control register 0 (TMC0)
The TMC0 register is an 8-bit register for controlling the count operation of 8-bit timer 3 (TM3).
The higher 4 bits control the count operation of TM3 of 8-bit timer/counter 3. (The lower 4 bits control the count
operation of TM0 of the 16-bit timer/counter.)
The TMC0 register allows both read and write operations using an 8-bit manipulation instruction. Fig. 7-123
shows the format of the TMC0 register.
When the RESET signal is applied, the TMC0 register is cleared to 00H.
Fig. 7-123 Format of Timer Control Register 0 (TMC0)
7 6 5 4 3 2 1 0
TMC0 CE3 CE0 0 0 0 OVF0 0 0
Clears and stops counting
Enables counting
0
1
TM3 counting control
These bits control counting for 16-bit timer/counter
(TM0) (see Fig. 7-3).
CE3
(2) Prescaler mode register 0 (PRM0)
The PRM0 register is an 8-bit register used to specify a count clock for 8-bit timer 3 (TM3).
The PRM0 register allows only write operation using an 8-bit manipulation instruction. Fig. 7-124 shows the
format of the PRM0 register.
When the RESET signal is applied, the PRM0 register is cleared to 00H.
Fig. 7-124 Format of Prescaler Mode Register 0 (PRM0)
Remark f
CLK
: System clock frequency
×: 1 or 2
7 6 5 4 3 2 1 0
PRM0 PRS3 0
PRS3
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 Ч Ч Ч
PRS1 PRS2 Specification of count clock [Hz]
f
CLK
/16
f CLK /32
f CLK /64
f CLK /128
f CLK /256
f CLK /512 85.3 s
42.7 s
21.3 s
10.7 s
5.3 s
1.3 s
Resolution
f CLK = 6 MHz
PRS2 PRS1 PRS0 0 0 0
PRS0
f CLK /8
2.6 s
Not to be set
µ
µ
µ
µ
µ
µ
µ