M38504M6-201FP 데이터 시트보기 (PDF) - MITSUBISHI ELECTRIC

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M38504M6-201FP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI ELECTRIC  

MITSUBISHI MICROCOMPUTERS

3850 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

NOTES ON PROGRAMMING

Processor Status Register

The contents of the processor status register (PS) after a reset are

undefined, except for the interrupt disable flag (I) which is “1.” After

a reset, initialize flags which affect program execution. In particu-

lar, it is essential to initialize the index X mode (T) and the decimal

mode (D) flags because of their effect on calculations.

Interrupts

The contents of the interrupt request bits do not change immedi-

ately after they have been written. After writing to an interrupt

request register, execute at least one instruction before performing

a BBC or BBS instruction.

Decimal Calculations

• To calculate in decimal notation, set the decimal mode flag (D)

to “1”, then execute an ADC or SBC instruction. After executing

an ADC or SBC instruction, execute at least one instruction be-

fore executing a SEC, CLC, or CLD instruction.

• In decimal mode, the values of the negative (N), overflow (V),

and zero (Z) flags are invalid.

Timers

If a value n (between 0 and 255) is written to a timer latch, the fre-

quency division ratio is 1/(n+1).

Multiplication and Division Instructions

• The index X mode (T) and the decimal mode (D) flags do not af-

fect the MUL and DIV instruction.

• The execution of these instructions does not change the con-

tents of the processor status register.

Ports

The contents of the port direction registers cannot be read. The

following cannot be used:

• The data transfer instruction (LDA, etc.)

• The operation instruction when the index X mode flag (T) is “1”

• The addressing mode which uses the value of a direction regis-

ter as an index

• The bit-test instruction (BBC or BBS, etc.) to a direction register

• The read-modify-write instructions (ROR, CLB, or SEB, etc.) to a

direction register.

Use instructions such as LDM and STA, etc., to set the port direc-

tion registers.

Serial I/O

In clock synchronous serial I/O, if the receive side is using an ex-

ternal clock and it is to output the SRDY signal, set the transmit

enable bit, the receive enable bit, and the SRDY output enable bit

to “1.”

Serial I/O continues to output the final bit from the TXD pin after

transmission is completed.

When an external clock is used as synchronous clock in serial I/O,

write transmission data to the transmit buffer register while the

transfer clock is “H.”

A-D Converter

The comparator uses capacitive coupling amplifier whose charge

will be lost if the clock frequency is too low.

Therefore, make sure that f(XIN) is at least on 500 kHz during an

A-D conversion.

Do not execute the STP or WIT instruction during an A-D conver-

sion.

Instruction Execution Time

The instruction execution time is obtained by multiplying the fre-

quency of the internal clock φ by the number of cycles needed to

execute an instruction.

The number of cycles required to execute an instruction is shown

in the list of machine instructions.

The frequency of the internal clock φ is half of the XIN frequency in

high-speed mode.

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