C8051F2XX Datasheet, PDF (66/146 Pages) Silicon Laboratories – Mixed Signal 8 kB ISP Flash MCU Family

C8051F2xx
PROGRAM MEMORY
0x207F
0x2000
0x1FFF
0x1E00
0x1DFF
128 Byte ISP FLASH
RESERVED
FLASH
(In-System
Programmable in 512
Byte Sectors)
0x0000
0xFF
0x80
0x7F
0x30
0x2F
0x20
0x1F
0x00
DATA MEMORY
Upper 128 RAM
(Indirect Addressing
Only)
Special Function
Register's
(Direct Addressing Only)
(Direct and Indirect
Addressing)
Bit Addressable
General Purpose
Registers
Lower 128 RAM
(Direct and Indirect
Addressing)
0x3FF
1024 Byte
XRAM
Mapped into
External Data Memory
Space
(C8051F226/236/206 only)
0x000
Figure 9.2. Memory Map
9.2.3. General Purpose Registers
The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of gen-
eral-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only
one of these banks may be enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 9.4). This allows
fast context switching when entering subroutines and interrupt service routines. Indirect addressing
modes use registers R0 and R1 as index registers.
9.2.4. Bit Addressable Locations
In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20
through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from
0x00 to 0x7F. Bit 0 of the byte at 0x20 has bit address 0x00 while bit 7 of the byte at 0x20 has bit address
0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit access is distinguished from a full byte access
by the type of instruction used (bit source or destination operands as opposed to a byte source or destina-
tion).
The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where
XX is the byte address and B is the bit position within the byte. For example, the instruction:
MOV
C, 22h.3
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the user Carry flag.
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Rev. 1.6