Programmer's Model And Cpu Registers; Accumulator (A) - NXP Semiconductors MC9S08SU16 Reference Manual

Programmer's Model and CPU Registers

• Indexed relative to H:X — Five submodes including auto increment
• Indexed relative to SP — Improves C efficiency dramatically
• Memory-to-memory data move instructions with four address mode combinations
• Overflow, half-carry, negative, zero, and carry condition codes support conditional
branching on the results of signed, unsigned, and binary-coded decimal (BCD)
operations
• Efficient bit manipulation instructions
• STOP and WAIT instructions to invoke low-power operating modes
10.2 Programmer's Model and CPU Registers
Figure 10-1 shows the five CPU registers. CPU registers are not part of the memory map.
CONDITION CODE REGISTER

10.2.1 Accumulator (A)

The A accumulator is a general-purpose 8-bit register. One input operand from the
arithmetic logic unit (ALU) is connected to the accumulator, and the ALU results are
often stored into the A accumulator after arithmetic and logical operations. The
128
7
ACCUMULATOR
16-BIT INDEX REGISTER H:X
8 7
15
INDEX REGISTER (H) INDEX REGISTER (X)
15
STACK POINTER
15
PROGRAM COUNTER
7
V 1 1 H I N Z
Figure 10-1. CPU Registers
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
0
A
0
0
SP
0
PC
0
C CCR
CARRY
ZERO
NEGATIVE
INTERRUPT MASK
HALF-CARRY (FROM BIT 3)
TWO'S COMPLEMENT OVERFLOW
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