UPD17708 datasheet(47/356 Pages) NEC

47 / 356 page

µPD17704, 17705, 17707, 17708, 17709

5.3.2 Function of address register

The address register specifies a program memory address when the table reference instruction (“MOVT DBF,

@AR”), stack manipulation instruction (“PUSH AR”, “POP AR”), indirect branch instruction (“BR @AR”), or

indirect subroutine call instruction (“CALL @AR”) is executed.

A dedicated instruction (“INC AR”) is available that can increment the contents of the address instruction by

one.

The following paragraphs (1) through (5) describe the operation of the address register when the respective

instructions are executed.

(1) Table reference instruction (“MOVT DBF, @AR”)

When the table reference instruction is executed, the constant data (16 bits) of a program memory

address specified by the contents of the address register are read to the data buffer.

The constant data that can be specified by the address register is stored to address 0000H to 1FFFH

in the case of

µPD17704, address 0000H to 2FFFH in the case of the µPD17705 and 17707, and address

0000H to 3FFFH in the case of the

µPD17708 and 17709.

(2) Stack manipulation instruction (“PUSH AR”, “POP AR”)

When the “PUSH AR” instruction is executed, the value of the stack pointer is decremented by one, and

the contents of the address register (AR) are transferred to an address stack register specified by the

stack pointer whose value has been decremented by one.

When the “POP AR” instruction is executed, the contents of an address stack register specified by the

stack pointer are transferred to the address register, and the value of the stack pointer is incremented

by one.

(3) Indirect branch instruction (“BR @AR”)

When this instruction is executed, the program branches to a program memory address specified by the

contents of the address register.

The branch address that can be specified by the address register is 0000H to 1FFFH in the case of

µPD17704, 0000H to 2FFFH in the case of the µPD17705 and 17707, and 0000H to 3FFFH in the case

of the

µPD17705 and 17708 and 17709.

(4) Indirect subroutine call instruction (“CALL @AR”)

The subroutine at a program memory address specified by the contents of the address register can be

called.

The first address of the subroutine that can be specified by the address register is 0000H to 1FFFH in

the case of the

µPD17704, 0000H to 2FFFH in the case of the µPD17705 and 17707, and 0000H to 3FFFH

in the case of the

µPD17708 and 17709.

(5) Address register increment instruction (“INC AR”)

This instruction increments the contents of the address register by one.

5.3.3 Address register and data buffer

The address register can transfer data as part of the peripheral hardware via the data buffer.

For details, refer to 9. DATA BUFFER (DBF).

UPD17708 Datasheet(PDF) 47 Page - NEC

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