ST7LITE20F2 ST7LITE25F2 ST7LITE29F2
6
Central processing unit
Central processing unit
6.1
6.2
6.3
Introduction
This CPU has a full 8-bit architecture and contains six internal registers allowing efficient
8-bit data manipulation.
Main features
● 63 basic instructions
● Fast 8-bit by 8-bit multiply
● 17 main addressing modes
● Two 8-bit index registers
● 16-bit stack pointer
● Low power modes
● Maskable hardware interrupts
● Non-maskable software interrupt
CPU registers
The 6 CPU registers shown in Figure 10 are not present in the memory mapping and are
accessed by specific instructions.
Figure 10. CPU registers
7
0
Reset value = XXh
7
0
Reset value = XXh
7
0
Reset value = XXh
15
PCH
87
PCL
0
Reset value = reset vector @ FFFEh-FFFFh
7
0
1 1 1 HI NZ C
Reset value = 1 1 1 X 1 X X X
15
87
0
Reset value = stack higher address
Accumulator
X index register
Y index register
Program counter
Condition code register
Stack pointer
X = Undefined value
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