HMS38112 Datasheet, PDF (31/73 Pages) List of Unclassifed Manufacturers – 4-BIT SINGLE CHIP MICROCOMPUTERS

Chapter 3. Architecture
Data Memory (RAM)
Ø Ø 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 4-2 shows the
configuration.
D0 D9 R0 R3 REMOUT
Output port
Data memory page (0~1)
01
23
Page 0
Page 1
4 a₀~a₃
Y-register (Y)
15
01
X-register (X)
Fig 3-2 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 reserved.
X1=0
X1=1
Y=0
D0
Reserved
Y=1
D1
Reserved
Table 3-1 Mapping table between X and Y register
Y-register (Y)
Y-register has 4 bits. It operates as a data pointer or a general-purpose register.
Y-register specifies an address (a₀~a₃) in a page of data memory, as well as it
is used to specify an output port. Further it is used to specify a mode of carrier
signal outputted from the REMOUT port. It can also be treated as a general-
purpose register on a program.
3-3