M16CSLASH1N datasheet(89/238 Pages) RENESAS

89 / 238 page

Rev.1.00

Oct 20, 2004

page 77 of 222

M16C/1N Group

12. Timers

REJ09B0007-0100Z

b5 b4

Timer X mode register

TXMOD0

TXMOD1

Operation mode

select bit 0, 1

(Note 1)

1 0 : Event counter mode

R0EDG

CNTR0 polarity

switching bit (Note 1)

0 : Counts at rising edge (Interrupt at rising edge)

1 : Counts at falling edge (Interrupt at falling edge)

TXS

Timer X count

start flag

0 : Stops counting

1 : Starts counting

TXMOD2

0 : Set to "0" in event counter mode

TXOCNT

0 : Set to "0" in event counter mode

Symbol

TXMR

Address

008B16

When reset

0016

Function

Bit name

Bit symbol

b1 b0

P30/TXOUT

select bit

Operation mode

select bit 2

TXEDG

Effectual edge

reception flag

TXUND

Timer X under

flow flag

Invalid in event counter mode.

When write, set "0". When read, this contents

is indeterminate.

Invalid in event counter mode.

When write, set "0". When read, this contents

is indeterminate.

Note 1: This bit should rewrite with inhibiting the CNTR0 interrupt. When using the interrupt, the interrupt must be enabled

after clearing the CNTR0 interrupt request bit to "0" using a MOV instruction.

Table 12.5 Specifications of event counter mode

(n+1) X (m+1)

Item

Specification

Count source

External signals fed to CNTR0 pin (Active edge is selected by software)

Count operation

• Down count

• When the timer underflows, it reloads the reload register contents before continuing

counting

Divide ratio

n: Set value of Prescaler X, m: Set value of Timer X

Count start condition

Count start flag is set (=1)

Count stop condition

Count start flag is reset (=0)

Interrupt request generation timing • When Timer X underflows [Timer X interruption]

• Rising (R0EDG=0) or falling (R0EDG=1) of CNTR0 input [CNTR0 interruption]

CNTR0 pin function

Count source input

TXOUT pin function

Programmable I/O port

Read from timer

Count value can be read out by reading Timer X register.

Same applies to Prescaler X register.

Write to timer

When a value is written to Timer X register, it is written to both reload register and counter.

Same applies to Prescaler X register.

Select function

• CNTR0 polarity switching function

The active edge of count source can be selected to be the rising or the falling edge with

software.

Figure 12.8 Timer X mode register in event counter mode

12.2.3 Event Counter Mode

In this mode, the timer counts an external signal fed to CNTR0 pin. (See Table 12.5) Figure 12.8

shows Timer X mode register in event counter mode.

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