S3C8245/P8245/C8249/P8249 ADDRESS SPACES
2-5
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 S3C8245/C8249 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.
Register Page Pointer (PP)
DFH ,Set 1, R/W
LSBMSB .7 .6 .5 .4 .3 .2 .1 .0
Destination register page selection bits:
0000 Destination: Page 0
Source register page selection bits:
0000 Source: Page 0
NOTE:
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.
Figure 2-3. Register Page Pointer (PP)
+ PROGRAMMING TIP — Using the Page Pointer for RAM clear (Page 0, Page 1)
LD PP,#00H ;Destination 0, Source 0
SRP #0C0H
LD R0,#0FFH ;Page 0 RAM clear starts
RAMCL0 CLR @R0
DJNZ R0,RAMCL0
CLR @R0 ;R0 = 00H
LD PP,#10H ;Destination 1, Source 0
LD R0,#0FFH ;Page 1 RAM clear starts
RAMCL1 CLR @R0
DJNZ R0,RAMCL1
CLR @R0 ;R0 = 00H
NOTE: You should refer to page 6-39 and use DJNZ instruction properly when DJNZ instruction is used in your program.