R8CSLASH15 datasheet(109/277 Pages) RENESAS

109 / 277 page

R8C/14 Group, R8C/15 Group

13. Timers

Rev.2.10

Jan 19, 2006

Page 97 of 253

REJ09B0164-0210

Figure 13.10

Operating Example in Pulse Period Measurement Mode

Underflow Signal of

Prescaler X

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 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 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.

0Fh 0Eh 0Dh 0Ch 0Bh 0Ah 09h 08h 0Fh 0Eh 0Dh

01h 00h 0Fh 0Eh

0Fh

0Eh

0Fh

0Ah

0Dh

01h

0Fh 0Eh

08h

TXS Bit in TXMR

TXEDG Bit in

TXMR Register

“1”

“0”

CNTR0i Pin Input

Contents of Timer X

Contents of

Read-Out Buffer1

IR Bit in

TXIC Register

IR Bit in INT1IC

TXUND Bit in

TXMR Register

Set to “1” by program

Starts

counting

Timer X

reloads

Retained

Timer X read(3)

Retained(7)

Set to “0” by program(4)

(2)

(6)

(7)

Timer X read(3)

Timer X

reloads

Timer X

reloads

Set to “0” by program(5)

Set to “0” when interrupt request is acknowledged, or set by program

“1”

“0”

“1”

“0”

“1”

“0”

“1”

“0”

“1”

“0”

00h

09h

0Eh

Conditions: A period from one rising edge to the next rising edge of measurement pulse is measured (R0EDG=0)

with the default value of the TX register as 0Fh.

i=0 to 1

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