EM78P451WM datasheet(9/54 Pages) EMC

9 / 54 page

EM78P451

8-Bit Microcontroller with OTP ROM

Product Specification (V1.1) 06.30.2003

• 5

(This specification is subject to change without further notice)

"CALL" instruction loads the lower 10 bits of the PC, and then PC+1 is pushed into

the stack. Thus, the subroutine entry address can be located anywhere within a

page

"RET" ("RETL k", "RETI") instruction loads the program counter with the contents

at the top of stack.

"MOV R2, A" allows the loading of an address from the "A" register to the lower 8

bits of PC, and the ninth and tenth bits (A8~A9) of PC are cleared.

"ADD R2, A" allows a relative address be added to the current PC, and the ninth

and tenth bits of PC are cleared.

Any instruction that is written to R2 (e.g. "ADD R2, A", "MOV R2, A", "BC R2,6",

⋅⋅⋅⋅⋅)

(except "TBL") will cause the ninth and tenth bits (A8~A9) of PC to be cleared.

Thus, the computed jump is limited to the first 256 locations of any program page.

"TBL" allows a relative address be added to the current PC (R2+A

→R2), and

contents of the ninth and tenth bits (A8~A9) of PC are not changed. Thus, the

computed jump can be on the second (or third, 4th) 256 locations on one program

page.

In case of EM78P451, the most significant bits (A10~A11) will be loaded with the

contents of bits PS0~PS1 in the status register (R3) upon the execution of a "JMP",

"CALL", or any other instructions which writes to R2.

All instructions are single instruction cycle (fclk/2 or fclk/4) except for the instruction

that would change the contents R2. Such instruction will need one more instruction

cycle.

A11A10

A9A8

A7 ~ A0

CALL

RET

RETL

RETI

Stack 1

Stack 2

Stack 3

Stack 4

Stack 5

000

3FF

Page 0

400

7FF

Page 1

800

BFF

Page 2

C00

FFF

Page 3

001:Hareware interrupt location

002:Software interrupt (INT instruction) location

FFF:Reset location

Fig. 3 Program Counter Organization

EM78P451WM Datasheet(PDF) 9 Page - ELAN Microelectronics Corp

EM78P451WM Datasheet(HTML) 9 Page - ELAN Microelectronics Corp

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

Datasheet Download

Link URL