ATAR080 datasheet(5/68 Pages) ATMEL

5 / 68 page

ATAR080

4675D–4BMCU–12/04

Figure 5. RAM Map

Registers

The microcontroller has seven programmable registers and one condition code register

(see Figure 6).

Program Counter (PC)

The program counter is a 12-bit register which contains the address of the next instruc-

tion to be fetched from ROM. Instructions currently being executed are decoded in the

instruction decoder to determine the internal micro-operations. For linear code (no calls

or branches), the program counter is incremented with every instruction cycle. If a

branch-, call-, return-instruction or an interrupt is executed, the program counter is

loaded with a new address. The program counter is also used with the table instruction

to fetch 8-bit wide ROM constants.

Figure 6. Programming Model

RAM

FCh

00h

FFh

03h

04h

Expression

stack

Return

stack

Global

variables

07h

(256

× 4-bit)

Autosleep

Global

variables

Expression Stack

Return Stack

TOS-1

TOS-2

TOS-1

TOS

4-bit

12-bit

Program Counter

Return Stack Pointer

Expression Stack Pointer

RAM Address Register (X)

RAM Address Register (Y)

Top of Stack Register

Condition Code Register

Carry/borrow

Branch

Interrupt enable

Reserved

TOS

CCR

ATAR080 Datasheet(PDF) 5 Page - ATMEL Corporation

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