M34551 View Datasheet(PDF) - MITSUBISHI ELECTRIC

Part Name

Description

Manufacturer

M34551

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for INFRARED REMOTE CONTROL TRANSMITTER

MITSUBISHI ELECTRIC  

MITSUBISHI MICROCOMPUTERS

4551 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for

INFRARED REMOTE CONTROL TRANSMITTER

TIMERS

The 4551 Group has the programmable timers.

q Programmable timer

The programmable timer has a reload register and enables

the frequency dividing ratio to be set. It is decremented from a

set value n. When it underflows (count to n + 1), a timer interrupt

request flag is set to “1,” new data is loaded from the reload

register, and count continues (auto-reload function).

q Fixed dividing frequency timer

The fixed dividing frequency timer has the fixed frequency

dividing ratio (n). An interrupt request flag is set to “1” every n

count of a count pulse.

FF16

n : Counter initial value

Count starts

Reload

n

1st underflow

Reload

2nd underflow

0016

Timer 1 interrupt “1”

request flag

“0”

n+1 count

n+1 count

Time

An interrupt occurs or

a skip instruction is executed.

Fig. 18 Auto-reload function

The 4551 Group timer consists of the following circuits.

• Prescaler : frequency divider

• Timer 1 : 8-bit programmable timer

• Timer 2 : 14-bit fixed dividing frequency timer

• Timer LC : 4-bit programmable timer

(Timers 1 and 2 have the interrupt function, respectively)

Prescaler, timer 1, timer 2 and timer LC can be controlled with

the timer control registers W1, W2 and W3.

Each function is described below.

Table 9 Function related timers

Circuit

Structure

Count source

Prescaler

Timer 1

Timer 2

Frequency divider • Instruction clock (INSTCK)

8-bit programmable • Prescaler output (ORCLK)

binary down counter • Carrier generating circuit

output (CARRY, CARRY/2)

14-bit fixed dividing • Prescaler output (ORCLK)

frequency

• f(XCIN)

Timer LC

4-bit programmable • Bit 3 of timer 2

binary down counter • System clock (STCK)

Frequency

dividing ratio

Use of output signal

4, 8

• Timer 1 and 2 count sources

1 to 256

• Timer 1 interrupt

• Port CARR output control

Control

register

W1

W1

W2

16384

• Timer 2 interrupt

W2

• Divider for LCD

• Watchdog timer

1 to 16

• Divider for LCD

W3

• Carrier output

18

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