GMS34004 Datasheet, PDF (20/105 Pages) Hynix Semiconductor – 4-BIT SINGLE CHIP MICROCOMPUTERS

Chapter 2. Architecture
Data memory (RAM)
Up to 32 nibbles (16 words ¡¿ 2pages ¡¿ 4bits) is incorporated for storing data.
The whole data memory area is indirectly specified by a data pointer (X,Y). Page
number is specified by zero bit of X register, and words in the page by 4 bits in
Y-register. Data memory is composed in 16 nibbles/page. Figure 2.2 shows the
configuration.
D0 D9 R0 R3 REMOUT
Output port
Data memory page (0~1)
01
23
Page 0
Page 1
15
4 A0~A3
Y-register (Y)
01
X-register (X)
4
2
Fig 2-2 Composition of Data Memory
X-register (X)
X-register is consist of 2bit, X0 is a data pointer of page in the RAM, X1 is only
used for selecting of D8~D9 with value of Y-register
X1=0
X1=1
Y=0
D0
D8
Y=1
D1
D9
Table 2-1 Mapping table between X and Y register
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