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M38B57MC Fiches technique(PDF) 60 Page - Mitsubishi Electric Semiconductor |
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M38B57MC Fiches technique(HTML) 60 Page - Mitsubishi Electric Semiconductor |
60 / 69 page MITSUBISHI MICROCOMPUTERS 38B5 Group SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER 60 PRELIMINAR Y Notice: This is not a final specification. Some parametric limits are subject to change. 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 particular, 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 immediately after they have been written. After writing to an interrupt request reg- ister, 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. Only the ADC and SBC instructions yield proper decimal results. After executing an ADC or SBC instruction, execute at least one instruction before ex- ecuting 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 affect the MUL and DIV instruction. •The execution of these instructions does not change the contents 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 register 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 direction registers. Serial I/O •Using an external clock When using an external clock, input “H” to the external clock input pin and clear the serial I/O interrupt request bit before executing serial I/O transfer and serial I/O automatic transfer. •Using an internal clock When using an internal clock, set the synchronous clock to the in- ternal clock, then clear the serial I/O interrupt request bit before ex- ecuting a serial I/O transfer and serial I/O automatic transfer. A-D Converter The comparator uses internal capacitors whose charge will be lost if the clock frequency is too low. Therefore, make sure that f(XIN) is at least on 250 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 frequency of the internal system clock by the number of cycles needed to ex- ecute an instruction. The number of cycles required to execute an instruction is shown in the list of machine instructions. The frequency of the internal system clock is the same of the XIN frequency in high-speed mode. At STP Instruction Release At the STP instruction release, all bits of the timer 12 mode register are cleared. The XCOUT drivability selection bit (the CPU mode register) is set to “1” (high drive) in order to start oscillating. NOTES ON USE Notes on Built-in EPROM Version The P47 pin of the One Time PROM version or the EPROM version functions as the power source input pin of the internal EPROM. Therefore, this pin is set at low input impedance, thereby being af- fected easily by noise. To prevent a malfunction due to noise, insert a resistor (approx. 5 k Ω) in series with the P47 pin. |
Numéro de pièce similaire - M38B57MC |
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Description similaire - M38B57MC |
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