7733 datasheet(137/940 Pages) RENESAS

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TIMER A

7733 Group User’s Manual

6–26

(1) Switching between countup and countdown

A register named “up-down flag” (address 4416) or pin TAiOUT’s input signal switches countup from

and to countdown. This switching is performed by an up-down flag when the up-down switching factor

selection bit (bit 4 at addresses 5616 to 5A16) = “0” and by pin TAiOUT’s input signal when the up-down

switching factor selection bit = “1.”

When the switching between countup and countdown is set while counting is in progress, this switching

is realized at the next valid edge of the count source.

s When switching by up-down flag

Countdown is performed when the up-down flag = “0,” and countup is performed when the up-down

flag = “1.” Figure 6.4.6 shows the structure of the up-down flag.

s When switching by pin TAiOUT’s input signal

Countdown is performed when pin TAiOUT’s input signal level is “L” and countup is performed when

it is “H.”

When switching countup from and to countdown by pin TAiOUT’s input signal, set a port P5 or P6

direction register’s bit which corresponds to pin TAiOUT for the input mode.

6.4 Event counter mode

Fig. 6.4.6 Structure of up-down flag

Bit

Bit name

At reset

Functions

Up-down flag (address 4416)

Timer A4 up-down flag

Timer A3 up-down flag

Timer A2 up-down flag

Timer A1 up-down flag

Timer A0 up-down flag

Timer A2 two-phase pulse signal

processing selection bit

Timer A3 two-phase pulse signal

processing selection bit

Timer A4 two-phase pulse signal

processing selection bit

0: Countdown

1: Countup

This bits is valid when the contents

of the up-down flag is selected as

the up-down switching factor.

0: Two-phase pulse signal

processing function is disabled.

1: Two-phase pulse signal

processing function is enabled.

When not using the two-phase pulse

signal processing function, be sure

to set this bit to “0.”

This bit is “0” at reading.

Note: When writing to bits 5 to 7, use the LDM or STA instruction.

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