at85c51snd3b ATMEL Corporation, at85c51snd3b Datasheet - Page 37

• Manufacturer Part Number: at85c51snd3b
• Description: Single-chip Digital Audio Decoder - Encoder With Usb 2.0 Interface
• Manufacturer: ATMEL Corporation

Special Function Registers
SFR Pagination
7632C–MP3–11/06
The AT85C51SND3B derivatives implement a SFR pagination mechanism which allows
mapping of high number of peripherals in the SFR space. As shown in Figure 24, four
pages are accessible through the PPCON (Peripheral Pagination Control) register (see
Table 37). The four bits of PPCON: PPS0 to PPS3 are used to select one page as
detailed in Table 36. Setting one bit of PPCON using the setb instruction automatically
clears the 7 others: e.g. if page 0 is selected, selecting page 3 is done by the instruction
setb PPS3 which clears PPS0.
By default, after reset selected page is page 0.
The PPCON content is automatically saved in a specific stack at each interrupt service
routine entry during vectorization and restored at exit during reti execution.
Figure 24. SFR Pagination Block diagram
Table 36. Page Selection Truth Table
Table 37. PPCON Register
PPCON (Y.C0h) – Peripheral Page Control Register
Reset Value = 0000 0001b
Number
PPS3
7-4
3-0
Bit
7
X
X
X
-
0
1
PPCON.0
PPCON.1
PPCON.2
PPCON.3
PPS0
PPS1
PPS2
PPS3
Mnemonic Description
PPS3:0
PPS2
Bit
6
-
-
0
X
X
1
0
Reserved
The value read from these bits is always 0. Do not set these bits.
Peripheral Page Select Bits
Refer to Table 36 for page decoding information.
PPS1
5
-
0
X
1
0
0
2
4
PPS0
-
0
1
0
0
0
Page 0
Page 0
Page 1
Page 2
Page 3
PPS3
3
0
AT85C51SND3B
1
PPS2
2
Selected Page
2
3
PPS1
1
PPS0
0
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