ATAR092 datasheet(4/107 Pages) ATMEL

4 / 107 page

4535E–4BMCU–05/07

ATAR092/ATAR892

4.2

Components of MARC4 Core

The core contains ROM, RAM, ALU, program counter, RAM address registers, instruction

decoder and interrupt controller. The following sections describe each functional block in more

detail.

4.2.1

ROM

The program memory (ROM) is mask programmed with the customer application program dur-

ing the fabrication of the microcontroller. The 4 Kbyte ROM size is addressed by a 12-bit wide

program counter. An additional 1 Kbyte of ROM exists which is reserved for quality control

self-test software The lowest user ROM address segment is taken up by a 512-byte zero page

which contains predefined start addresses for interrupt service routines and special subroutines

accessible with single byte instructions (SCALL).

The corresponding memory map is shown in Figure 4-2 Look-up tables of constants can also be

held in ROM and are accessed via the MARC4’s built-in table instruction.

Figure 4-2.

ROM Map

4.2.2

RAM

The ATAR092 and ATAR892 contain 256 x 4-bit wide static random access memory (RAM). It is

used for the expression stack, the return stack and data memory for variables and arrays. The

RAM is addressed by any of the four 8-bit wide RAM address registers SP, RP, X and Y.

4.2.2.1

Expression Stack

The 4-bit wide expression stack is addressed with the expression stack pointer (SP). All arith-

metic, I/O and memory reference operations take their operands from, and return their results to

the expression stack. The MARC4 performs the operations with the top of stack items (TOS and

TOS-1). The TOS register contains the top element of the expression stack and works in the

same way as an accumulator. This stack is also used for passing parameters between subrou-

tines and as a scratch pad area for temporary storage of data.

ROM

(4 K x 8 Bit)

FFFh

7FFh

1FFh

000h

1F8h

1F0h

1E8h

1E0h

020h

018h

010h

008h

000h

140h

180h

040h

0C0h

008h

$AUTOSLEEP

$RESET

INT0

INT1

INT2

INT3

INT4

INT5

INT6

INT7

1E0h

1C0h

100h

080h

page

000h

Zero

Zero Page

ATAR092 Datasheet(PDF) 4 Page - ATMEL Corporation

ATAR092 Datasheet(HTML) 4 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL