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155
CHAPTER 8 16-BIT TIMER/EVENT COUNTERS 00, 01
User
’
s Manual U14260EJ3V1UD
(4) Prescaler mode register 0n (PRM0n: n = 0, 1)
This register is used to set the 16-bit timer counter 0n (TM0n) count clock and TI00n, TI01n pin input valid edges.
PRM0n is set by an 8-bit memory manipulation instruction.
RESET input clears PRM0n to 00H.
Figure 8-12. Format of Prescaler Mode Register 00 (PRM00)
Address: FF61H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
PRM00
ES110
ES100
ES010
ES000
0
0
PRM010
PRM000
ES110
ES100
TI010 pin valid edge selection
0
0
Falling edge
0
1
Rising edge
1
0
Setting prohibited
1
1
Both falling and rising edges
ES010
ES000
TI000 pin valid edge selection
0
0
Falling edge
0
1
Rising edge
1
0
Setting prohibited
1
1
Both falling and rising edges
PRM010
PRM000
Count clock selection
f
X
= 8.38 MHz
f
X
= 12 MHz
Note 1
0
0
f
X
8.38 MHz
12 MHz
0
1
f
X
/2
2
2.09 MHz
3 MHz
1
0
f
X
/2
6
130 kHz
187 kHz
1
1
TI000 pin valid edge
Notes 2, 3
Notes 1.
Expanded-specification products of
μ
PD780078 Subseries only.
2.
The external clock requires a pulse two cycles longer than internal clock (f
X
/2
3
).
3.
When the valid edge of the TI000 pin is selected, the main system clock is used as the sampling clock
for noise elimination. The valid edge of the TI000 pin can be used only when the main system clock
is operating.
Cautions 1. Always set data to PRM00 after stopping the timer operation.
2. If the valid edge of the TI000 pin is to be set as the count clock, do not set the clear & start
mode and the capture trigger at the valid edge of the TI000 pin.
3. When P70 is used as the valid edge of the TI000 pin, it cannot be used as the timer output
(TO00 pin), and when used as the TO00 pin, it cannot be used as the valid edge of the TI000
pin.
4. If the TI000 or TI010 pin is high level immediately after system reset, the rising edge is
immediately detected after the rising edge or both the rising and falling edges are set as
the valid edge(s) of the TI000 pin or TI010 pin to enable the operation of 16-bit timer counter
00 (TM00). Be careful when pulling up the TI000 pin or the TI010 pin. However, when re-
enabling operation after the operation has been stopped once, the rising edge is not
detected.
Remarks 1.
f
X
: Main system clock oscillation frequency
2.
TI000 or TI010 pin: 16-bit timer/event counter 00 input pin