Datasheet

Central processing unit ST7LITE20F2 ST7LITE25F2 ST7LITE29F2
30/170 DocID8349 Rev 7
6 Central processing unit
6.1 Introduction
This CPU has a full 8-bit architecture and contains six internal registers allowing efficient
8-bit data manipulation.
6.2 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
6.3 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
Accumulator
X index register
Y index register
Stack pointer
Condition code register
Program counter
70
1C11HI NZ
Reset value = reset vector @ FFFEh-FFFFh
70
70
70
0
7
15 8
PCH
PCL
15
8
70
Reset value = stack higher address
Reset value =
1X11X1XX
Reset value = XXh
Reset value = XXh
Reset value = XXh
X = Undefined value