E0C6001 TECHNICAL SOFTWARE
II-32
• Bit-unit operation of the display memory
Label
Mnemonic/operand
Comment
LD
X,SEGBUF
;
Set address display
;
memory buffer
LD
Y,090H
;
Set address display memory
LD
MX,3
;
Set buffer data
LD
MY,MX
;
SEG-A, B ON (
●
●
,
▲
▲
)
AND
MX,1110B
;
Change buffer data
LD
MY,MX
;
SEG-A OFF (
●
,
▲
▲
)
AND
MX,1101B
;
Change buffer data
LD
MY,MX
;
SEG-B OFF (
●
,
▲
)
For manipulation of the display memory in bit-units for the
assignment of Figure 3.5.5, a buffer must be provided in
RAM to hold data. Note that, since the display memory is
write-only, data cannot be changed directly using an ALU
instruction (for example, AND or OR).
After manipulating the data in the buffer, write it into the
corresponding display memory using the transfer command.
Fig. 3.5.5
Example of segment
assignment
▲
●
090H
D3
D2
D1
D0
Address
Data
▲
●
: SEG-A
: SEG-B