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MSM66573 Family User's Manual
Chapter 2 CPU Architecture
Each segment is assigned an internal segment offset address of 0 to 0FFFFH. The address
calculation to determine the addressed target is performed with a 16-bit offset address and
any resulting overflow or underflow is ignored, so TSR does not change. The TSR value
at reset is 00H.
(3)
Data segment register (DSR)
DSR specifies the segment in data memory space to which the data currently in use
belongs. DSR is an 8-bit register and is assigned to the SFR area. The contents of DSR
can be overwritten by instructions that use SFR addressing. Only bits 0 to 3 of DSR are
valid. If read, a value of "0" will be obtained for bits 4 to 7. If writing to DSR, "0" must be
written to bits 4 to 7.
2.4
Addressing Modes
The MSM66573 family has two independent memory spaces, the data memory space and
the program memory space.
Addressing can be roughly classified into two modes,
corresponding to each memory space.
The data memory space is referred to as "RAM space", since it normally consists of random
access memory (RAM). The addressing for this space is referred to as "RAM addressing".
The program memory space is referred to as "ROM space", since it normally consists of
read-only memory (ROM).
The addressing for this space is referred to as "ROM
addressing".
ROM addressing is classified as immediate addressing contained in instruction codes,
table data addressing for data (normally read-only data) in a ROM space table, and program
code addressing for programs in the ROM space.
ROM window addressing is a unique method of addressing. It involves accessing table
data in the ROM space using the above RAM addressing methods. Data in a table segment
is read through a data segment window specified and opened by the program.
2.4.1 RAM Addressing
This addressing mode specifies addresses for program variables in the RAM space.
Available addressing formats include: register addressing, page addressing, direct
addressing, pointing register indirect addressing and special bit area addressing.
"0"
76543210
DSR
00000000
At reset
"0" indicates that a value of "0" must be written.
If read, a value of "0" will be obtained.
Address: 0009 [H]
R/W access: R/W