AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 24

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

Figure 2-1
2.1.1
Figure 2-2
2-2
Addressable
Register Name
Register Set
Processor Status Flags Register
The 16-bit processor Status Flags register (Figure 2-2) records specific characteristics of
the result of logical and arithmetic instructions (bits 0, 2, 4, 6, 7, and 11) and controls the
operation of the microcontroller within a given operating mode (bits 8, 9, and 10).
After an instruction is executed, the value of the flags may be set (to 1), cleared/reset (set
to 0), unchanged, or undefined. The term undefined means that the flag value prior to the
execution of the instruction is not preserved, and the value of the flag after the instruction
is executed cannot be predicted.
Processor Status Flags Register (F)
Bits 15–12—Reserved
Bit 11: Overflow Flag (OF)—Set if the signed result cannot be expressed within the number
of bits in the destination operand; cleared otherwise.
Bit 10: Direction Flag (DF)—Causes string instructions to auto-decrement the appropriate
index registers when set. Clearing DF causes auto-increment.
Register
Shown)
Names
(8-Bit
Byte
16-Bit
AX
DX
CX
BX
BP
SP
SI
DI
15
Reserved
7
15
Destination Index
Source Index
Base Pointer
AH
DH
CH
BH
Registers
General
0 7
OF
SF
TF
ZF
DF
IF
AL
DL
CL
BL
Programming
0
0
7
Special Register
Multiply/Divide
I/O Instructions
Loop/Shift/Repeat/Count
Stack Pointer
Index Registers
Res
Base Registers
Functions
AF
Res
PF
Res
CF
0
Register Name
FLAGS
16-Bit
IP
CS
DS
SS
ES
15
15
Processor Status Flags
Status and Control
Segment Registers
Instruction Pointer
Code Segment
Data Segment
Stack Segment
Extra Segment
Registers
0
0