Sharp MZ-80B Owner's Manual page 53

44
4.2.3 Memory map for V-RAM accessing state
The memory addresses are changed over also when accessing the V-RAM . The RAM addresses in
normal state are from $0000 to $7FFF for RAM
(1),
and from $8000 to $FFFF for RAM (II). In the
case of V-RAM access, addressing of $DOOO to $FFFF in RAM (II) is disabled, so that the V-RAM will
be the object of access.
This changeover is effected by A
7
of PIO. When two pages of graphic V-RAM are used , selection
of graphic pages
(I)
and (II) will be done by OUT port $F4. This operation is shown in FIGURE 4.4.
Address
$0000
r - - - - - - - - - - - , - - ,
RAM I Adr.
$7FFF
$8000
1 - - - - - - - - + - - - 1
RAM IT
(Option)
Adr.
$CFFFL-----~~
~{ Swit,hing by PIO A,
1
$DOOO
.--------,-.....1---,
I
v
RAM I I
$DFFF
RAM ll
Adr.
Ch~racter
IAdr.l
'-------......__,__,
~
/Switohing by OUT pmt $F4
$EOOO
RAM IT Adr1
$FFFFL-----~~
V-RAM
Graphic
I
(Option)
Page
1
Adr.
V-RAM
Graphic ll
(Option)
Page 2
FIGURE 4.4
Switching of main memory and V-RAM (1)
Adr.
The address switching of V -RAM shown above is effected by the monitor subroutine PRINT or the
like.