UPD75238GJ

Manufacturer Part NumberUPD75238GJ
Description4 BIT SINGLE-CHIP MICROCOMPUTER
ManufacturerNEC [NEC]
UPD75238GJ datasheet
 
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3.3 DATA MEMORY (RAM)
The data memory consists of a static RAM and peripheral hardware.
The static RAM consists of an area of 768 words 4 bits in memory banks 0, 2, and 3, an area of 160 words
4 bits in memory bank 1, and an area of 96 words
data memory. The RAM is used for storing processing data, and is also used as stack memory for subroutine
and interrupt execution.
To particular memory addresses, general registers, display data memory, and peripheral hardware (various
registers) are mapped. Data in these areas are manipulated using general register manipulation instructions
and memory manipulation instructions (See Fig. 2-1).
As a stack area, all addresses in memory banks 0, 1, 2, and 3 (000H to 3FFH) can be used.
The data memory has a configuration of 4 bits per address, but allows 8-bit memory manipulation
instructions to be used for 8-bit oriented manipulation, and also allows bit manipulation instructions to be
used for bit-by-bit manipulation. Even addresses are to be specified for 8-bit manipulation instructions.
Fig. 3-4 shows the organization of the display data memory area (1A0H to 1FFH).
Stack
area
Display
data
memory,
Data area
etc.
Static RAM
(1024
4)
4 bits in memory bank 1, which is used also as display
Fig. 3-3 Data Memory Map
Data memory
000H
General
register
(32
4)
area
01FH
020H
256
4
0FFH
100H
256
4
19FH
1A0H
(96
4)
1FFH
200H
256
4
2FFH
300H
256
4
3 FFH
Not contained
F80H
Peripheral
128
4
hardware area
FFFH
PD75238
Memory bank
0
1
2
3
15
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