MSM6442 查看數據表（PDF） - Oki Electric Industry

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MSM6442

Built-in LCD Driver 4-Bit Microcontroller

Oki Electric Industry 

¡ Semiconductor

MSM6442

NOTES ON USE

Notes on Using Ports 5 and 6 of MSM6442

The MSM6442 uses Port 5 (P5) and Port 6 (P6) to rewrite the display in the LCD and the

dedicated registers in LCD section, and to read the interrupt indication flag.

Writing and reading is completed when data has been written using P5 and P6, in this order

successively. Therefore, if an interrupt occurs during operation of P5 and P6 and these ports are

operated by the interrupt routine, the MSM6442 may not operate normally.

Countermeasure

Disable a process interruption during operation of P5 and P6. Make the program interrupt

disabled when rewriting the display in LCD, rewriting a dedicated register such as the system

control register (SCR), or reading/resetting the interrupt indication flag. Note that the program

examples provided in the User's Manual use the assumption that each program is in the

interrupt disabled state. Therefore, when executing any of the program examples in the

interrupt enabled state, execute the MDI and MEI instructions according to the following

examples:

(1) Writing data into a dedicated register

LAI m Set write data m

MDI

Disable interrupt (*1)

OPD 6

LAI n Set control command n

OPD 5

MEI

Enable interrupt (*2)

RPBD 5, 3 End of write processing

(2) Reading the interrupt indication flag

LAI 0FH

MDI

Disable interrupt (*1)

OPD 6

LAI 0AH Set control command 0AH

OPD 5

IPD 6 Read flag

MEI

Enable interrupt (*2)

RPBD 5, 3 End of read processing

*1 If an accumulator is not saved during interrupt processing, the MDI instruction must be

executed before the LAI instruction is executed.

*2 During actual processing, an interrupt is enabled after the execution of the RPBD 5, 3

instruction.

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