7721 datasheet(169/577 Pages) RENESAS

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TIMER B

7721 Group User’s Manual

9–2

9.1 Overview

Timer B consists of three counters, Timers B0 to B2, each equipped with a 16-bit reload function. Timers

B0 to B2 operate independently of one another.

Timer B has three operating modes listed below. Timers B0 and B1 have selective three operating modes

listed below. Timer B2 operates only in the timer mode.

(1)

Timer mode (Timers B0 to B2)

The timer counts an internally generated count source.

(2)

Event counter mode (Timers B0 and B1)

The timer counts an external signal.

(3)

Pulse period/Pulse width measurement mode (Timers B0 and B1)

The timer measures an external signal’s pulse period or pulse width.

In this chapter, Timer Bi (i = 0 to 2) indicates Timers B0 to B2. Timer Bj (j = 0, 1) indicates Timers B0 and

B1; this is used when the timer B’s input/output pins are used etc. (Hereafter, input/output pins are called

I/O pins.)

9.2 Block description

Figure 9.2.1 shows the block diagram of Timer B. Explanation of registers relevant to Timer B is described

below.

9.1 Overview 9.2 Block description

f 2

f 16

f 64

f 512

Count source select bits

Timer mode

Pulse period/Pulse width measurement mode

Polarity switching

and edge pulse

generating circuit

Event counter

mode

Count start bit

Counter reset circuit

Data bus (odd)

Data bus (even)

(Low-order 8 bits)

(High-order 8 bits)

Timer Bi reload register (16)

Timer Bi counter (16)

Timer Bi

interrupt

request bit

TBj IN

Timer Bj

overflow

flag

(Valid in pulse period/pulse width

measurement mode)

i = 0–2, j = 0, 1

Fig. 9.2.1 Block diagram of Timer B

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