T48C893 datasheet(9/82 Pages) ATMEL

9 / 82 page

T48C893

Rev. A4, 22-Jan-02

9 (82)

RAM

FCh

00h

Autosleep

FFh

03h

04h

TOS–1

Expression

stack

Return

stack

Global

variables

07h

(256 x 4-bit)

Global

variables

4-bit

TOS

TOS–1

TOS–2

Expression stack

Return stack

12-bit

94 8975

Figure 5. RAM map

3.2.3

Registers

The

MARC4 controller has seven programmable

registers and one condition code register. They are shown

in the following programming model.

Program Counter (PC)

The program counter (PC) is a 12-bit register which

contains the address of the next instruction to be fetched

from the 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.

TOS

CCR

–– B

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

Figure 6. Programming model

T48C893 Datasheet(PDF) 9 Page - ATMEL Corporation

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