Zilog Z80380 - Manual (Page 25)

3-3
Z380 ™
U SER ' S M ANUAL Z ILOG
DC-8297-03
The Z380 CPU implements one instruction to switch to
Extended mode from Native mode; SETC XM (set Ex-
tended mode) places the Z380 CPU in Extended mode. Once in Extended mode, only Reset can return it to Native
mode. On Reset, the Z380 is in Native mode. Refer to
Sections 4 and 5 for more examples.
3.4 WORD AND LONG WORD MODE OF OPERATION
The Z380 CPU can operate in either Word or Long Word
mode. In Word mode (the Reset configuration), all word
operations manipulate 16-bit quantities, and are compat-
ible with the Z80 CPU 16-bit operations. In the Long Word
mode, all word operations can manipulate 32-bit quanti-
ties. Note that the Native/Extended and Word/Long Word
selections are independent of one another, as Word/Long
Word pertains to data and operand address manipulation
only. The Z380 CPU implements two instructions and two
decoder directives to allow switching between these two
modes; SETC LW (Set Long Word) and RESC LW (Reset
Long Word) perform a global switch, while DDIR LW and
DDIR W are decoder directives that select a particular
mode only for the instruction that they precede.
Examples:
1. Effect of Word mode and Long Word mode
DDIR W
LD
BC, (HL)
Loads BC15-BC0 from the location (HL) and
(HL+1), and BCz (BC31-BC16) remains un-
changed.
DDIR LW
LD
BC, (HL)
Loads BC31-BC0 from the locations (HL) to (HL+3).
2. Immediate data load with DDIR instructions
DDIR IW,LW
LD
HL,12345678H
Loads 12345678H into HL31-HL0.
DDIR IB,LW
LD
HL,123456H
Loads 00123456H into HL31-HL0.
00H is appended as the Most significant byte as
HL31-HL24.
DDIR LW
LD
HL,1234H
Loads 00001234H into HL31-HL0.
0000H is appended as the HL31-HL16 portion.
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