Configuration Basics
2-2
Am186™CC/CH/CU Microcontrollers User’s Manual
These registers are grouped into the following categories:
■
General-Purpose registers: Eight 16-bit general-purpose registers support arithmetic
and logical operands. Four of these (AX, BX, CX, and DX) also operate as pairs of
separate 8-bit registers (AH, AL, BH, BL, CH, CL, DH, and DL). The Destination Index
(DI) and Source Index (SI) general-purpose registers support data movement and string
instructions. The Base Pointer (BP) and Stack Pointer (SP) general-purpose registers
point to the bottom and to the top of the stack frame (in the stack segment), respectively.
– Base and Index registers: Four of the general-purpose registers (BP, BX, DI, and
SI) also support the determination offset addresses of operands in memory. These
registers can contain base addresses or indexes to particular locations within a
segment. The addressing mode selects the specific registers for operand and address
calculations.
– Stack Pointer register: All stack operations (POP, POPA, POPF, PUSH, PUSHA,
PUSHF) utilize the stack pointer. The Stack Pointer (SP) register is always offset from
the Stack Segment (SS) register, and no segment override is allowed.
■
Segment registers: Four 16-bit special-purpose registers (CS, DS, ES, and SS) select,
at any given time, the segments of memory that are immediately addressable for code
(CS), data (DS and ES), and stack (SS) memory.
■
Status and Control registers: Two 16-bit special-purpose registers record or alter
certain aspects of the processor state—the Instruction Pointer (IP) register contains the
offset address of the next sequential instruction to be executed, and the Processor Status
Flags (FLAGS) register contains status and control flag bits (see Figure 2-1 and Figure
2-2).
Figure 2-1
Register Set
2.2.2
Processor Status Flags Register
The 16-bit Processor Status Flags register, illustrated in 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).
AH
Byte
Addressable
(8-Bit
Register
Names
Shown)
Loop/Shift/Repeat/Count
Base Registers
Code Segment
Data Segment
Stack Segment
Extra Segment
Processor Status Flags
Instruction Pointer
General
Registers
Status and Control
Registers
Segment Registers
15 0
15 0
7 0
7 0
15 0
CS
FLAGS
IP
16-Bit
Register Name
Special Register
Functions
DS
SS
ES
AX
DX
CX
BX
BP
SI
DI
SP
DH
CH
BH
AL
DL
CL
BL
Index Registers
Stack Pointer
Multiply/Divide
I/O Instructions
Base Pointer
Source Index
Destination Index
16-Bit
Register Name
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...