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Page Mode, allowing from zero to three automatic wait states for the same-page accesses
in the Page Mode. The third setting selects from five to nine automatic wait states for
memory-write bus cycles. The choices available for the advanced bus wait states are suffi-
cient to allow interfacing to a variety of standard memories for any Rabbit 4000 speed
grade.
When a 16-bit memory is connected to /CS0, the first few instructions must program the
device to operate in 16-bit mode. This code is shown below. This code should be the first
thing executed by your device. Because the processor is fetching bytes from a 16-bit
memory device that is not connected to A0, only one-byte instructions can be used, and
they must occur in pairs.
ORG
0000h
XOR
A
; a <= 00000000
XOR
A
LD
H, A
; h <= 00000000
LD H,
A
SCF
SCF
RLA
; a <= 00000001
RLA
; a <= 00000010
LD
B, A
; b <= 00000010
LD B,
A
SCF
SCF
ADC
A, B
; a <= 00000101
ADC
A, B
; a <= 00000111
ADD
A, A
; a <= 00001110
ADD
A, A
; a <= 00011100
SCF
SCF
ADC
A, H
; a <= 00011101
ADC
A, H
LD
L, A
; l <= 00011101
LD L,
A
IOI ; two IOIs same as one
IOI
LD
(HL), B
; MACR <= 00000010
LD
(HL), B
; dummy memory write (no /WE)
NOP ; required delay to start
NOP ; up the 16-bit bus
Summary of Contents for Rabbit 4000
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