EM78P451SWM datasheet(34/54 Pages) EMC

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EM78P451S

8-Bit Microcontroller with OTP ROM

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Product Specification (V1.0) 06.01.2004

(This specification is subject to change without further notice)

4.6 Timer 1

4.6.1 Overview

Timer1(TMR1) is an eight-bit clock counter with a programmable prescaler. It is

designed for the SPI module as a baud rate clock generator. TMR1 can be read and

written and cleared on any reset conditions. If employed, it can be turned down for

power saving by setting TMR1EN bit [T1CON<2>] to 0.

4.6.2 Function description

Fig. 15 shows TIMER1 block diagram. Each signal and block is described as follows:

Comarator

PWP

TMR1

increase

reset

Sets TMR1IF

Clock output

Prescaler

1:1 to 1:16

OSC/4

OSC/2

Fig. 15 TIMER1 Block Diagram

OSC/4:Input clock.

Prescaler: Option of 1:1, 1:4, 1:8, and 1:16 defined by T1P1 and T1P02

(T1CON<1, 0>). It is cleared when a value is written to TMR1 or T1CON, and

during any kind of reset as well.

PWP: Pulse width preset register. The desired width of baud clock is written in

advance.

TMR1: Timer 1 register. TMR1 increases until it matches with PWP, and then

resets to 0. If it is chosen optionally in the SPI mode, its output is fed as a shifting

clock.

Comparator: To change the output status while a match occurs. The TMR1IF flag

will be set at the same time.

4.6.3 Programmed the related registers

The related registers of the defining TMR1 operation are shown in Table 4 and Table 5

Table 4 Related Control Registers of the TMR1

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0x0C

SPIS/RC

TM1IF

OD3

OD4

RBFIF

RBF

0x0F

INTC/IOCF

TM1IE

SPIIE

EXIE

TCIE

Table 5 Related Status/Data Registers ofTMR1

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0X0E

TMR1/RE

TMR17

TMR16

TMR15

TMR14

TMR13

TMR12

TMR11

TMR10

0x0F

PWP/RF

PWP7

PWP6

PWP5

PWP4

PWP3

PWP2

PWP1

PWP0

0x0C

T1CON/IOCC

TM1E

TM1P1

TM1P0

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