Sharp ER-A750 Service Manual page 55

3. Address map
3-1. Total memory space
The address map of the total memory space is shown below. As you
can see, the memory space is divided into the following 5 blocks:
•
0page area (including the I/O area)
•
VRAM
•
RAM
•
ROM
•
Extended I/O area
*The low-order 32 KB of the ROM area and the low
-order approximately 32 KB of the RAM area are
mapped over the 0page area. By mapping the ROM
area,it is possible to accommodate vector addressing
processes including reset start.
000000h
0 page area
(64KB)
00FFFFh
100000h
VRAM
(512KB)
180000h
RAM
(9.5MB)
C00000h
ROM
(3MB)
F00000h
Extended I/O area
(1MB)
FFFFFFh
*The extended I/O area is a space for I/O devices
which are to be addressed in spaces other than the
0page area.In the MPCA7,the addresses from
FFFF00h to FFFFFFh are used for the SSP's addd-
ressing register.
Fig. 2
3-2. 0page area
The 0page area consists of four spaces: the ROM mapped area,
RAM mapped area, internal and external I/O areas.
The ROM and RAM mapped spaces have been devised for the fol-
lowing purposes:
1 Simplifying the procedure for booting the IPL program
2 Separating the static RAM access from file space.
3 Achieving high-speed accessing, and accessing by abbreviated
instructions.
* In the ER-A750, the low-order 32 KB of the RASP space (180000h
1FFFFFh) is mapped (With the MPCA7's internal registers
RASPE=1 and RASEL=0, the address line MA15 should be
used.)
*The addresses from C00000h to C07FFFh (the low-
order 32 KB of the ROS1) are mappd over the ROM
mapped are.
000000h
ROM mapping area
080000h
RAM mapping area
00FE80h
Internal I/O area
00FF80h
External I/O area
00FFFFh
*If the MPCA7's address line MA15 is used with the
MPCA7's internal register RASPE=1, the addresses
from 180000h to 187E7Fh (about less than 32 KB)
of the RASP space are mapped over the 0page area.
7 – 25
I/O area
Fig. 3