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EM73962A

4-BIT MICROCONTROLLER

ELAN Microelectronics 

EM73962A

4-BIT MICROCONTROLLER

PROGRAM COUNTER (16K ROM) for EM73962A

Program counter ( PC ) is composed by a 13-bit counter, which indicates the next executed address for the

instruction of program ROM.

For a 8K - byte size ROM, PC can indicate address form 0000h - 1FFFh, for BRANCH and CALL instrcutions,

PC is changed by instruction indicating.

(1) Branch instruction:

SBR a

Object code: 00aa aaaa

Condition: SF=1; PC ← PC 12-6.a ( branch condition satisified )

PC Hold original PC value+1 a a a a a a

SF=0; PC← PC +1( branch condition not satisified )

PC

Original PC value + 1

LBR a

Object code: 1100 aaaa aaaa aaaa

Condition: SF=1; PC ← PC 12.a ( branch condition satisified )

PC

Hold

+2

a

aa

a

a

aa a a a a a

SF=0; PC← PC +2( branch condition not satisified )

PC

Original PC value + 2

SLBR a

Object code: 0101 0101 1100 aaaa aaaa aaaa (a:1000h~1FFFh)

0101 0111 1100 aaaa aaaa aaaa (a:0000h~0FFFh)

Condition: SF=1; PC ← a ( branch condition satisified)

PC a a a a a a a a a a a a a

SF=0 ; PC ← PC + 3 ( branch condition not satisified )

PC

Original PC value + 3

(2) Subroutine instruction:

SCALL a

Object code: 1110 nnnn

Condition : PC ← a ; a=8n+6 ; n=1..Fh ; a=86h, n=0

PC 0 0 0 0 0 a a a a a 1 1 0

LCALL a

Object code: 0100 0aaa aaaa aaaa

Condition: PC ← a

* This specification are subject to be changed without notice.

10.8.2001 8

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