ST72F63 STMICROELECTRONICS [STMicroelectronics], ST72F63 Datasheet - Page 14

• Manufacturer Part Number: ST72F63
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST7263B
5 CENTRAL PROCESSING UNIT
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
5.3 CPU REGISTERS
The 6 CPU registers shown in
present in the memory mapping and are accessed
by specific instructions.
Figure 7. CPU Registers
14/132
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
RESET VALUE = STACK HIGHER ADDRESS
RESET VALUE = RESET VECTOR @ FFFEh-FFFFh
15
15
RESET VALUE = 1
PCH
8 7
8
RESET VALUE = XXh
RESET VALUE = XXh
RESET VALUE = XXh
7
7
7
7
1
7
1 1 X 1 X X
1 1 H I
Figure 7
PCL
N Z
are not
0
0
0
0
X
0
0
C
Accumulator (A)
The Accumulator is an 8-bit general purpose reg-
ister used to hold operands and the results of the
arithmetic and logic calculations and to manipulate
data.
Index Registers (X and Y)
In indexed addressing modes, these 8-bit registers
are used to create either effective addresses or
temporary storage areas for data manipulation.
(The Cross-Assembler generates a precede in-
struction (PRE) to indicate that the following in-
struction refers to the Y register.)
The Y register is not affected by the interrupt auto-
matic procedures (not pushed to and popped from
the stack).
Program Counter (PC)
The program counter is a 16-bit register containing
the address of the next instruction to be executed
by the CPU. It is made of two 8-bit registers PCL
(Program Counter Low which is the LSB) and PCH
(Program Counter High which is the MSB).
ACCUMULATOR
X INDEX REGISTER
Y INDEX REGISTER
PROGRAM COUNTER
CONDITION CODE REGISTER
STACK POINTER
X = Undefined Value