Register Page Pointer (Pp) - Samsung S3C8275X User Manual

ADDRESS SPACES

REGISTER PAGE POINTER (PP)

The S3C8-series architecture supports the logical expansion of the physical 256-byte internal register file (using
an 8-bit data bus) into as many as 16 separately addressable register pages. Page addressing is controlled by
the register page pointer (PP, DFH). In the S3C8275X/C8278X/C8274X microcontroller, a paged register file
expansion is implemented for LCD data registers, and the register page pointer must be changed to address
other pages.
After a reset, the page pointer's source value (lower nibble) and the destination value (upper nibble) are always
"0000", automatically selecting page 0 as the source and destination page for register addressing.
MSB
Destination register page selection bits:
0000 Destination: Page 0
0001 Destination: Page 1 (Not used for the S3C8278X/C8274X)
0010 Destination: Page 2
others Not used for the S3C8275X/C8278X/C8274X
NOTES:
1. In the S3C8275X microcontroller, the internal register file is configured as three pages (Pages 0-2).
The pages 0-1 are used for general purpose register file, and page 2 is used for LCD data register or
general purpose register.
2. In the S3C8278X/C8274X microcontroller, the internal register file is configured as two pages (Pages 0, 2).
The page 0 is used for general purpose register file, and page 2 is used for LCD data register or general
purpose register.
3. A hardware reset operation writes the 4-bit destination and source values shown above to the register page
pointer. These values should be modified to address other pages.
2-8
Register Page Pointer (PP)
DFH, Set 1, R/W
.7 .6 .5 .4
Figure 2-5. Register Page Pointer (PP)
S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
.3 .2 .1 .0
Source register page selection bits:
0000 Source: Page 0
0001 Source: Page 1 (Not used for the S3C8278X/C8274X)
0010 Source: Page 2
others Not used for the S3C8275X/C8278X/C8274X
LSB