NJU3101 데이터 시트보기 (PDF) - Japan Radio Corporation

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NJU3101

4-BIT SINGLE CHIP TINY CONTROLLER

Japan Radio Corporation  

NJU3101

• PROGRAM COUNTER(PC)

PROGRAM COUNTER(PC) consisted of the 9-bit binary counter stores the address for the next

operating instruction in ROM. Data figures limited from b0 to b5 on the PC indicate the address in a

page, and data figures limited from b6 to b8 on the PC indicate the page in ROM. Although the ROM

address can be indicated 512 addresses continuously, the target address of JMP instruction is restricted

by Paging structure in ROM.

The PC condition is set to “0” on the “RESET” operation.

(MSB) 8

7

6

5

4

3

2

1

0 (LSB)

Page allocation

Address location

JMP instruction can branch to the optional address in the page. The target address is indicated by the

data figures limited from b0 to b5(6 bits) on PC as shown in above. The paging structure can reduce the

program size in ROM and the JMP instruction execution time against JPL instruction because JMP

instruction is consisted of one byte(8 bits) length. JPL and CALL instructions can branch to the optional

address without considering the paging structure, because they consist of two bytes(16 bits) length

including the 9 bits of PC.

• STACK

STACK consists of the 8 by 9 bits registers. It holds the data of PC automatically when the subroutine

call (CALL). PC gets the held data from STACK when the return (RET) operation.

[Structure of STACK]

STACK POINTER 8

0

000

PC

001

PC

010

PC

011

PC

100

PC

101

PC

110

PC

111

PC

• STACK POINTER(SP)

STACK POINTER(SP) consists of the 3 bits binary counter. SP indicates the number of next operating

position in the STACK. It counts one up(increment) after the subroutine call(CALL), and it counts one

down(decrement) after the return(RET) operation.

Data storing operation to STACK after that SP overflowed(over than 7) or under flowed(under than 0),

breaks the former held data in STACK. Therefore the subroutine nesting level must be cautioned in the

application program.

SP condition is set to "0" on “RESET” operation.

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