UPD70433GD-16-5BB NEC [NEC], UPD70433GD-16-5BB Datasheet - Page 21

• Manufacturer Part Number: UPD70433GD-16-5BB
• Description: V55PITM 16-BIT MICROPROCESSOR
• Manufacturer: NEC [NEC]

DS0 to another segment register. Also, in addressing which uses BP as the base register, another segment register can
be used instead of SS.
the offset for each register to (register bank number
3.2.5
segment registers which specify the start address of each 64K-byte segment of the 16M-byte extended memory space.
There are two extended segment registers, DS2 (Data Segment 2) and DS3 (Data Segment 3), which are used as shown
below.
the block transfer instruction, DS2 and DS3 can be specified simultaneously by segment override prefix. (In this case, the
order for DS2 and DS3 is optional.)
using another register or effective address for the specification of physical address, with the relative address from the start
address as the offset value.
However, using a segment override prefix instruction makes it possible for access of general variables to change from
When a reset is performed, PS of register bank 15 is initialized to FFFFH, and SS, DS0 and DS1 are initialized to 0000H.
These registers are mapped onto the register file space (in on-chip RAM). The address is the value obtained by adding
In addition to the segment registers for accessing the 1M-byte basic memory space, the V55PI is provided with extended
The data access using an extended semgnet register is performed by using the segment override prefix. Especially, in
The CPU specifies the start address of each segment with an extended segment register, and performs an access by
The physical address is created as shown in the next page.
Extended Segment Registers (DS2, DS3)
Example
DS2: Extended memory space general variable accesses (by segment override prefix instructions), source block
DS3: Extended memory space general variable accesses (by segment override prefix instructions), destination
Example
data accesses in extended memory space block transfer instructions, etc.
block data accesses in extended memory space block transfer instructions, etc.
MOV
MOV
MOV
REP
DS2:
DS3: MOVBKW ; Word memory block transfer from DS2 : IX to DS3 : IY.
AW, 1000H
DS1 : AW
BL, DS1, BYTE PTR [IX]; DSI : Byte data read from IX
Table 3-3. Segment Register Offsets
Register
DS0
DS1
SS
PS
32).
Offset
0EH
0AH
0CH
08H
PD70433
21