EM78P157NAAS datasheet(13/56 Pages) EMC

13 / 56 page

EM78P157N

8-Bit Microcontroller with OTP ROM

Product Specification (V1.0) 09.22.2005

• 7

(This specification is subject to change without further notice)

PC (A9 ~ A0)

Stack Level 1

Stack Level 3

Stack Level 2

Stack Level 4

Stack Level 5

On-chip Program

Memory

000H

3FFH

008H

Interrupt Vector

Reset Vector

Fig. 4-2 R2 (Program Counter) & Stack Organization

4.1.4 Status (R3) Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

GP2

GP1

GP0

Bit 0 (C):

Carry flag

Bit 1 (DC): Auxiliary carry flag

Bit 2 (Z):

Zero flag

Set to "1" if the result of an arithmetic or logic operation is zero

Bit 3 (P):

Power down bit

Set to “1” during power on or by a "WDTC" command

Reset to “0” by a "SLEP" command

Bit 4 (T):

Time-out bit

Set to “1” with the "SLEP" and "WDTC" commands, or during power up

Reset to “0” by WDT time-out

Bit 5~7 (GP0 ~ 2): General-purpose read/write bits

4.1.5 RAM Select (R4) Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Not used (read only)

Select Registers

Z flag of R3 will set to “1” when R4 content is equal to “3F.” When R4=R4+1, R4

content will function as R0. See the data memory configuration shown in Section 4.1.

Bits 0~5:

are used to select registers (Address: 00~06, 0F~3F) in indirect address

mode

Bits 6~7:

are not used (read only)

Bits 6~7 are set to “1” all the time

EM78P157NAAS Datasheet(PDF) 13 Page - ELAN Microelectronics Corp

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