7721 datasheet(147/577 Pages) RENESAS

147 / 577 page

TIMER A

7721 Group User’s Manual

8–28

8.4 Event counter mode

[Precautions for event counter mode]

1. While counting is in progress, by reading the timer Aj register, the counter value can be read out at any

timing. However, if the timer Aj register is read at the reload timing shown in Figure 8.4.9, the value

“FFFF16” (at an underflow) or “000016” (at an overflow) is read out. If reading is performed in the period

from when a value is set into the timer Aj register with the counter stopped until the counter starts

counting, the set value is correctly read out.

Fig. 8.4.9 Reading timer Aj register

2. The TAjOUT pin is used for all functions listed below. Accordingly, only one of these functions can be

selected for each timer.

•Switching between countup and countdown by TAjOUT pin’s input signal

•Pulse output function

•Two-phase pulse signal processing function

n – 1

Counter value

(Hex.)

FFFF n – 1

Read value

(Hex.)

Reload

Time

n = Reload register’s contents

(1) For countdown

FFFD FFFE FFFF

n + 1

FFFD FFFE FFFF 0000 n + 1

(2) For countup

Counter value

(Hex.)

Read value

(Hex.)

Reload

Time

n = Reload register’s contents

7721 Datasheet(PDF) 147 Page - Renesas Technology Corp