ST72324xx-Auto
5
Central processing unit (CPU)
Central processing unit (CPU)
5.1
Introduction
This CPU has a full 8-bit architecture and contains six internal registers allowing efficient 8-
bit data manipulation.
5.2
Main features
● Enable executing 63 basic instructions
Obsolete Product(s) - Obsolete Product(s) 5.3
● Fast 8-bit by 8-bit multiply
● 17 main addressing modes (with indirect addressing mode)
● Two 8-bit index registers
● 16-bit stack pointer
● Low power Halt and Wait modes
● Priority maskable hardware interrupts
● Non-maskable software/hardware interrupts
CPU registers
The six CPU registers shown in Figure 7 are not present in the memory mapping and are
accessed by specific instructions.
Figure 7. CPU registers
7
0
Reset value = XXh
7
0
Reset value = XXh
7
0
Reset value = XXh
15
PCH
87
PCL
0
Accumulator
X index register
Y index register
Reset value = reset vector @ FFFEh-FFFFh
Program counter
7
0
1 1 I1 H I0 N Z C
Reset value = 1 1 1 X 1 X X X
Condition code register
15
87
0
Reset value = stack higher address
Stack pointer
X = undefined value
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