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CPU Registers
3-4
RISC 16-Bit CPU
3.2 CPU Registers
The CPU incorporates sixteen 16-bit registers. R0, R1, R2 and R3 have
dedicated functions. R4 to R15 are working registers for general use.
3.2.1 Program Counter (PC)
The 16-bit program counter (PC/R0) points to the next instruction to be
executed. Each instruction uses an even number of bytes (two, four, or six),
and the PC is incremented accordingly. Instruction accesses in the 64-KB
address space are performed on word boundaries, and the PC is aligned to
even addresses. Figure 3−2 shows the program counter.
Figure 3−2. Program Counter
0
15 0
Program Counter Bits 15 to 1
1
The PC can be addressed with all instructions and addressing modes. A few
examples:
MOV #LABEL,PC ; Branch to address LABEL
MOV LABEL,PC ; Branch to address contained in LABEL
MOV @R14,PC ; Branch indirect to address in R14