W741C205 Просмотр технического описания (PDF) - Winbond

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W741C205

4-BIT MICROCONTROLLER

Winbond 

Preliminary W741C20X

FUNCTIONAL DESCRIPTION

Program Counter (PC)

Organized as an 11-bit binary counter (PC0 to PC10), the program counter generates the addresses

of the 2048 × 16 on-chip ROM containing the program instruction words. When jump or subroutine

call instructions or interrupt, or initial reset conditions are to be executed, the address corresponding

to the instruction will be loaded into the program counter. The format used is shown below.

ITEM

Initial Reset

INT 0 (Divider)

INT 1 (Timer 0)

INT 2 (Port RC)

INT 3 ( INT pin)

INT 4 (Serial Port Input)

INT 5 (Serial Port Output)

INT 6 (Timer 1)

JMP Instruction

Subroutine Call

ADDRESS

000H

004H

008H

00CH

014H

018H

01CH

020H

XXXH

XXXH

INTERRUPT

PRIORITY

-

1st

2nd

3rd

4th

5th

6th

7th

-

-

Stack Register (STACK)

The stack register is organized as 11 bits x 8 levels (first-in, last-out). When either a call subroutine or

an interrupt is executed, the program counter will be pushed onto the stack register automatically. At

the end of a call subroutine or an interrupt service subroutine, the RTN instruction must be executed

to pop the contents of the stack register into the program counter. When the stack register is pushed

over the eighth level, the contents of the first level will be lost. In other words, the stack register is

always eight levels deep.

Program Memory (ROM)

The read-only memory (ROM) is used to store program codes; the look-up table is arranged as 2048

× 4 bits. The first three quarters of ROM (000H to 5FFH) are used to store instruction codes only, but

the last quarter (600H to 7FFH) can store both instruction codes and the look-up table. Each look-up

table element is composed of 4 bits, so the look-up table can be addressed up to 2048 elements.

Instruction MOVC R is used to read the look-up table and transfer table data to the RAM. The

organization of the program memory is shown in Figure 1.

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