EMC EM78612 - page 13

EM78612

Universal Serial Bus Microcontroller

Product Specification (V1.0)03.2 2.2006 •

••

•11

(This specification is subject to change without further notice)

R2 (Program Counter & Stack) Default Value: (0B_0000_0000)

The EM78612 Program Counter is an 11-bit long register that allows access to 2K

bytes of Program Memory with 5 level stacks.The eight LSB bits, 00~07, are located at

R2, while the one MSB bits, 10, is located at R3 [5].The Program Counter is cleared

after Power-on reset or WatchDog reset. The first instruction that is executed after a

reset is located at Address 00h.

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Fig 7-2 The Structure of ROM Page

R3 (Status Register) Default Value:(0B_0001_1000)

7 6 5 4 3 2 1 0

- - PS0 T P Z DC C

R3 [0] Carry y/Borrow flag. For ADD , SUB Instructions

1 = A carry-out from the Most Significant bit of the result occurred

0 = No carry-out from the Most Significant bit of the result occurred

NOTE

For Borrow, the polarity is reversed.For rotate (RRC, RLC) instructions, this bit

is loaded with either the high or low-order bit of the source register

R3 [1] Auxiliary carry /borrow flag. For ADD , SUB Instructions

1 = A carry-out from the 4th low-order bit of the result occurred

0 = No carry-out from the 4th low-order bit of the result

NOTE

For Borrow, the polarity is reversed.

Stack1

Stack2

Stack3

Stack4

Stack5

07 06R3

R2 09 08 07 06 05 04 03 02 01 00

CALL

RET

RETL

RETI

PAGE0 0000 ~ 03FF

PAGE1 0400 ~ 07FF

04 03 02 01 00