upd70f3422gj-gae-qs-ax Renesas Electronics Corporation., upd70f3422gj-gae-qs-ax Datasheet - Page 123

• Manufacturer Part Number: upd70f3422gj-gae-qs-ax
• Description: 32-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

CPU System Functions
Figure 3-7
3.5.2 Recommended use of data address space
When accessing operand data in the data space, one register has to be used
for address generation. This register is called pointer register. With relative
addressing, an instruction can access operand data at all addresses that lie in
the range of ±32 KB relative to the address in the pointer register.
By this offset addressing method load/store instructions can be
accommodated in a single 32-bit instruction word, resulting in faster program
execution and smaller code size.
To enhance the efficiency of using the pointer in consideration of the memory
map, the following is recommended:
For efficient use of the relative addressing feature, the data segments should
be located in the address range FFFF F800
to 0000 7FFF
the upper bound, thus the registers and a part of the RAM can be addressed
via relative addressing, with base address 0 (r0).
It is recommended to locate flash memory data segments in the area up to
0000 7FFF
addressing.
Use the r0 register as pointer register for operand addressing. Since the r0
register is fixed to zero by hardware, it can be used as a pointer register and, at
the same time, for any other purposes, where a zero register is required. Thus,
no other general purpose register has to be reserved as pointer register.
Example application of wrap-around
Preliminary User’s Manual U17566EE1V2UM00
H
, so access to these constant data can utilize also relative
H
. The peripheral I/O registers and the internal RAM is aligned to
(r0=)0000 0000H
FFFF F000H
FFFF EFFFH
FFFF 8000H
FFFF 7FFFH
FFFF 0000H
0000 7FFFH
peripheral I/O area
Internal RAM area
Internal RAM area
Internal flash area
(28 KB)
(32 KB)
(1 MB)
(4 KB)
Fixed
H
to 0000 0000
+32 KB
-32 KB
H
and 0000 0000
Chapter 3
123
H