EMC EM78612 User Manual
Page 13
EM78612
Universal Serial Bus Microcontroller
Product Specification (V1.0) 03.22.2006
•••• 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.
Γ
Γ
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 06
R3
R2
09 08 07 06 05 04 03 02 01 00
E
CALL
RET
RETL
RETI
PAGE0
0000 ~ 03FF
PAGE1
0400 ~ 07FF
05
10
0
1
04 03 02 01 00