Motorola MC68HC908MR32 사용자 설명서
Central Processor Unit (CPU)
CPU Registers
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
Advance Information
MOTOROLA
Central Processor Unit (CPU)
75
6.4.4 Program Counter
The program counter (PC) is a 16-bit register that contains the address
of the next instruction or operand to be fetched.
of the next instruction or operand to be fetched.
Normally, the program counter automatically increments to the next
sequential memory location every time an instruction or operand is
fetched. Jump, branch, and interrupt operations load the program
counter with an address other than that of the next sequential location.
sequential memory location every time an instruction or operand is
fetched. Jump, branch, and interrupt operations load the program
counter with an address other than that of the next sequential location.
During reset, the program counter is loaded with the reset vector
address located at $FFFE and $FFFF. The vector address is the
address of the first instruction to be executed after exiting the reset state.
address located at $FFFE and $FFFF. The vector address is the
address of the first instruction to be executed after exiting the reset state.
6.4.5 Condition Code Register
The 8-bit condition code register (CCR) contains the interrupt mask and
five flags that indicate the results of the instruction just executed. Bits 6
and 5 are set permanently to logic 1. The functions of the condition code
register are described here.
five flags that indicate the results of the instruction just executed. Bits 6
and 5 are set permanently to logic 1. The functions of the condition code
register are described here.
Bit
15
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
Read:
Write:
Reset:
Loaded with vector from $FFFE and $FFFF
Figure 6-5. Program Counter (PC)
Bit 7
6
5
4
3
2
1
Bit 0
Read:
V
1
1
H
I
N
Z
C
Write:
Reset:
X
1
1
X
1
X
X
X
X = Indeterminate
Figure 6-6. Condition Code Register (CCR)