L9803 STMicroelectronics, L9803 Datasheet - Page 15

• Manufacturer Part Number: L9803
• Description: Super Smart Power Motor Driver With 8-bit Mcu, Ram, Eeprom, Adc, Wdg, Timers, Pwm And H-bridge Driver
• Manufacturer: STMicroelectronics

L9803
2
2.1
2.2
Central Processing Unit
Introduction
The CPU has a full 8-bit architecture. Six internal registers allow efficient 8-bit data
manipulation. The CPU is capable of executing 63 basic instructions and features 17 main
addressing modes.
CPU registers
The 6 CPU registers are shown in the programming model in
interrupt, all registers except Y are pushed onto the stack in the order shown in
They are popped from stack in the reverse order.
The Y register is not affected by these automatic procedures. The interrupt routine must
therefore handle Y, if needed, through the PUSH and POP instructions.
Accumulator (A). The Accumulator is an 8-bit general purpose register used to hold
operands and the results of the arithmetic and logic calculations as well as data
manipulations.
Index Registers (X and Y). These 8-bit registers are used to create effective addresses or
as temporary storage areas for data manipulation. The Cross-Assembler generates a
PRECEDE instruction (PRE) to indicate that the following instruction refers to the Y register.
Program Counter (PC). The program counter is a 16-bit register containing the address of
the next instruction to be executed by the CPU.
Figure 3.
CONDITION CODE REGISTER:
Organization of Internal CPU Registers
X = Undefined
X INDEX REGISTER:
Y INDEX REGISTER:
PROGRAM COUNTER:
ACCUMULATOR:
STACK POINTER:
RESET VALUE =0 0 0 0 0 0 0 1 0 1 1 1 1 1 1 1
RESET VALUE = RESET VECTOR @ FFFEh-FFFFh
15
15
0
0 0 0 0 0 0
1
RESET VALUE:
RESET VALUE:
RESET VALUE:
RESET VALUE:
X
X
X
7
7
7
7
1
7
1
7
Figure
X X X X X X
X X X X X X
X X X X X X
1 1 X 1 X X
1 1 H I
Central Processing Unit
3. Following an
N Z
0
X
0
X
0
X
0
0
0
X
C
Figure
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4.