R8C/13 Group
12.1 Timer (Timer X)
Underflow signal
of prescaler X
Set to "1" by program
“1”
“0”
TXS bit in
TXMR register
Starts counting
CNTR0 pin
input
“1”
“0”
Timer X
reloads
Timer X
reloads
Timer X
reloads
Timer X
contents
0E16
(7)
0F16
0F16
0F16 0E16 0D16 0C16 0B16 0A16 0916 0816 0F16 0E16 0D16
(7)
0116 0016 0F16 0E16
Retained
Retained
Contents of
read-out buffer
1
0016 0F16 0E16
0116
0E16
0A16 0916
0816
0D16
Timer X read
(3)
Timer X read
(3)
(2)
(2)
TXEDG bit in
TXMR register
“1”
“0”
Cleared to "0" by program
(4)
(6)
TXUND bit in
TXMR register
“1”
“0”
Cleared to "0" by program
(5)
IR bit in TXIC
register
“1”
“0”
Cleared to “0” when interrupt request is accepted, or cleared by program
IR bit in INT1IC
register
“1”
“0”
Cleared to “0” when interrupt request is accepted, or cleared by program
Conditions: A period from one rising edge to the next rising edge of measurement pulse is measured (R0EDG=0)
with TX register initial value=0F16
.
NOTES:
1. The contents of the read-out buffer can be read when the TX register is read in pulse period measurement mode.
2. After an active edge of measurement pulse is input, the TXEDG bit in the TXMR register is set to "1" (active edge found)
when the prescaler 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 is 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. When set to "0" by 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. When set to "0" by 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. The TXUND and TXEDG bits are both set to "1" if the timer 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 CNTR0 active edge is input, when the prescaler X underflow signal is "H" level, its count value is the one of the
read buffer. If "L" level, the following count value is the one of the read buffer.
Figure 12.10 Operation Example in Pulse Period Measurement Mode
Rev.1.20 Jan 27, 2006 page 79 of 205
REJ09B0111-0120
RENESAS [ RENESAS TECHNOLOGY CORP ]
