Renesas R8C/18 Series Hardware Manual page 130

R8C/18 Group, R8C/19 Group
Underflow signal of
prescaler X
TXS bit in TXMR
1
register
0
1
CNTR0i pin input
0
Contents of timer X
Contents of
read-out buffer1
TXEDG bit in
1
TXMR register
0
TXUND bit in
1
TXMR register
0
IR bit in
1
TXIC register
0
IR bit in INT1IC 1
register 0
Conditions: The period from one rising edge to the next rising edge of the measured pulse is measured (R0EDG = 0)
with the default value of the TX register as 0Fh.
i = 0 to 1
NOTES:
1. The contents of the read-out buffer can be read by reading the TX register in pulse period measurement mode.
2. After an active of edge the measured pulse is input, the TXEDG bit in the TXMR register is set to 1 (active edge found)
when the prescale X underflows for the second time.
3. The TX register should be read before the next active edge is input after the TXEDG bit is set to 1 (active edge found).
The contents in the read-out buffer are retained until the TX register is read. If the TX register is not read before the next active edge is
input, the measured result of the previous period is retained.
4. To set to 0 by a program, use a MOV instruction to write 0 to the TXEDG in the TXMR register. At the same time,
write 1 to the TXUND bit.
5. To set to 0 by a program, use a MOV instruction to write 0 to the TXUND in the TXMR register. At the same time,
write 1 to the TXEDG bit.
6. Bits TXUND and TXEDG are both set to 1 if timer X underflows and reloads on an active edge simultaneously.
In this case, the validity of the TXUND bit should be determined by the contents of the read-out buffer.
7. If the prescaler X underflow signal is "H" level when the CNTR0 active edge is input, the value in the read buffer is the count value at that
point. If the prescaler X underflow signal is "L" level when the CNTR0 active edge is input, the value in the read buffer is the next count
value.
Figure 14.10 Operating Example in Pulse Period Measurement Mode
Rev.1.30 Apr 14, 2006
REJ09B0222-0130
Set to 1 by program
Starts
counting
Timer X
reloads
0Fh 0Eh 0Fh 0Eh 0Dh 0Ch 0Bh 0Ah 09h 08h 0Fh 0Eh 0Dh
(7)
Retained
0Fh 0Eh
(2)
Set to 0 by program
Set to 0 when interrupt request is acknowledged, or set by program
Set to 0 when interrupt request is acknowledged, or set by program
Page 115 of 233
Timer X
reloads
(7)
Retained
0Ah 09h 08h 0Dh
(3)
Timer X read Timer X read
(2)
(4)
Set to 0 by program
14. Timers
Timer X
reloads
01h 00h 0Fh 0Eh
01h 00h 0Fh 0Eh
(3)
(Note 6)
(5)