UPD17708 datasheet(27/356 Pages) NEC

27 / 356 page

µPD17704, 17705, 17707, 17708, 17709

2.4.2 Subroutine

(1) Direct subroutine call (“CALL addr”)

The first address of a subroutine that can be called by the direct subroutine instruction is in page 0 of

each segment (addresses 0000H through 07FFH).

(2) Indirect subroutine call (CALL @AR)

The first addresses of a subroutine that can be called by the indirect subroutine call instruction are all

the addresses of the program memory, i.e., addresses 000H through 1FFFH for the

µPD17704,

addresses 0000H through 2FFFH for the

µPD17705, 17707, and 0000H through 3FFFH for the µPD17708

and 17709.

For further information, also refer to 5.3 Address Register (AR).

2.4.3 Table reference

The addresses that can be referenced by the table reference instruction (“MOVT DBF, @AR”) are all the

addresses of the program memory, i.e., addresses 0000H through 1FFFH for the

µPD17704, addresses 0000H

through 2FFFH for the

µPD17705, 17707, and 0000H through 3FFFH for the µPD17708 and 17709.

For further information, also refer to 5.3 Address Register (AR) and 9.2.2 Table reference instruction

(MOVT, DBF, @AR).

2.4.4 System call

The first address of a subroutine that can be called by the system call instruction (“SYSCAL entry”) is the

first 16 steps of each block (block 0 to 7) in page 0 of segment 1 (system segment).

Figure 2-4. Outline of System Call Instruction

Page 1

Page 2

Page 3

Page 0

(16 bits

× 2K steps)

(16 bits

× 8K steps)

Segment 0

Page 1

Page 2

Page 3

(16 bits

× 8K steps)

Segment 1

(system segment)

Block 0

Block 1

Block 2

Block 7

Block 0 of segment 1

Entry address of

SYSCAL instruction

020 F F H

02100 H

021 F F H

02200 H

022 F F H

02700 H

02000 H

0200 F H

Area where entry

address of system

segment can be

specified

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