NEC 78K0 User Manual page 133

(4) Prescaler mode register 00 (PRM00)
This register is used to set the 16-bit timer counter 00 (TM00) count clock and TI000 and TI010 input valid edges.
PRM00 can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears PRM00 to 00H.
Address: FFBBH After reset: 00H
Symbol 7
PRM00 ES101
ES101
0
0
1
1
ES001
0
0
1
1
PRM001
0
0
1
1
Note The external clock requires a pulse two cycles longer than internal clock (f
Cautions 1. When the Ring-OSC clock is selected as the clock to be supplied to the CPU, the clock of the
Ring-OSC oscillator is divided and supplied as the count clock. If the count clock is the
Ring-OSC clock, the operation of 16-bit timer/event counter 00 is not guaranteed. When an
external clock is used and when the Ring-OSC clock is selected and supplied to the CPU, the
operation of 16-bit timer/event counter 00 is not guaranteed, either, because the Ring-OSC
clock is supplied as the sampling clock to eliminate noise.
2. Always set data to PRM00 after stopping the timer operation.
3. If the valid edge of TI000 is to be set for the count clock, do not set the clear & start mode
using the valid edge of TI000 and the capture trigger.
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). Care is therefore required when pulling up the TI000 or TI010 pin. However, when re-
enabling operation after the operation has been stopped once, the rising edge is not
detected.
CHAPTER 6 16-BIT TIMER/EVENT COUNTER 00
Figure 6-8. Format of Prescaler Mode Register 00 (PRM00)
R/W
6 5
ES100 ES001
ES100
0 Falling edge
1 Rising edge
0 Setting prohibited
1 Both rising and falling edges
ES000
0 Falling edge
1 Rising edge
0 Setting prohibited
1 Both rising and falling edges
PRM000
0 f (10 MHz)
X
2
1 f /2 (2.5 MHz)
X
8
0 f /2 (39.06 kHz)
X
1 TI000 valid edge
User's Manual U16227EJ2V0UD
4 3 2
ES000 0 0
TI010 valid edge selection
TI000 valid edge selection
Count clock selection
Note
1 0
PRM001 PRM000
).
X
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