NEC uPD78076 User Manual

The memory to be manipulated in the fixed space is directly addressed with 8-bit data in an instruction word.

The fixed space to which this addressing is applied to is the 256-byte space, from FE20H to FF1FH.  An internal

high-speed RAM and a special function register (SFR) are mapped at FE20H to FEFFH and FF00H to FF1FH,

respectively.

The SFR area where short direct addressing is applied (FF00H to FF1FH) is a part of the SFR area.  In this  area,

ports which are frequently accessed in a program, a compare register of the timer/event counter, and a capture

register of the timer/event counter are mapped and these SFRs can be manipulated with a small number of bytes

and clocks.

When 8-bit immediate data is at 20H to FFH, bit 8 of an effective address is set to 0.  When it is at 00H to 1FH,

bit 8 is set to 1.  Refer to [Illustration] below.

Identifier

Description

saddr

Label of FE20H to FF1FH immediate data

saddrp

Label of FE20H to FF1FH immediate data (even address only)

 MOV 0FE30H, #50H;  when setting saddr to FE30H and immediate data to 50H

Operation code

0 0 0 1 0 0 0 1

OP code

0 0 1 1 0 0 0 0

30H (saddr-offset)

0 1 0 1 0 0 0 0

50H (immediate data)

When 8-bit immediate data is 20H to FFH, 

α

 = 0

When 8-bit immediate data is 00H to 1FH, 

α

 = 1

15

0

Short Direct Memory

Effective Address

1

1

1

1

1

1

1

8 7

0

7

OP code

saddr-offset

α