EM78451AP EMC [ELAN Microelectronics Corp], EM78451AP Datasheet - Page 9

• Manufacturer Part Number: EM78451AP
• Description: 8-Bit Microcontroller
• Manufacturer: EMC [ELAN Microelectronics Corp]

Product Specification (V1.2) 05.27.2004
(This specification is subject to change without further notice)
PC
4.1.4 R3 (Status Register)
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 and reset
Bit 4 (T) Time-out bit. Set to 1 with the "SLEP" and the "WDTC" commands, or during
Bits 5 (PS0) ~ 6 (PS1) Page select bits. PS0~PS1 are used to pre-select a program
GP
In the case of EM78451, the most significant bit (A10,A11) will be loaded with the
All instructions are single instruction cycle (fclk/2 or fclk/4) except for the instruction
content of bit PS0 ~PS1 in the status register (R3) upon the execution of a "JMP",
"CALL", or any other instructions which writes to R2.
that would change the contents of R2. Such instruction will need one more
instruction cycle.
7
A11A10
to 0 by a "SLEP" command.
power up and reset to 0 with WDT timeout.
memory page. When executing a "JMP", "CALL", or other instructions which
causes the program counter to be changed (e.g. MOV R2, A), PS0~PS1 are
loaded into the 11th and 12th bits of the program counter where it selects one
of the available program memory pages. Note that RET (RETL, RETI)
instruction does not change the PS0~PS1 bits. That is, the return will always
be the page from where the subroutine was called, regardless of the current
settings of PS0~PS1 bits. PS1 bit is not used (read as "0") and cannot be
modified in EM78451.
00
01
10
11
PS1
6
Fig. 3 Program counter organization
A9A8
BFF
FFF
3FF
7FF
C00
000
400
800
PS0
5
Page 1
Page 2
Page 0
Page 3
A7 ~ A0
4
T
002:Software interrupt (INT instruction) location
001:Hareware in terrupt location
FFF:Reset location
P
3
CALL
RET
RETL
RETI
Z
2
Stack 1
Stack 2
Stack 3
Stack 4
Stack 5
8-Bit Microcontroller
DC
1
EM78451
C
0
• 5