Hi,
In this post/chapter I would like to discuss about the general purpose and flag registers of 8080/8085... the following diagram would give you the big picture of the general purpose and flag registers of 8080/8085 micro processor.
| General Pupose and Flag Registers of 8080/8085 MicroProcessor |
| Accumulator (8-bit) |
|
7
S
|
6
Z
|
5
X
|
4
AC
|
3
X
|
2
P
|
1
X
|
0
C
|
|
| B (8-bit) | C (8-bit) |
| D (8-bit) | E (8-bit) |
| H (8-bit) | L (8-bit) |
| Stack Pointer(SP) (16-bit) |
| Program Counter(PC) (16-bit) |
| A small note on registers... |
| 1 |
an 8-bit Accumulator |
| 2 |
7 8-bit general purpose registers including accumulator |
| 3 |
16-bit general purpose register pairs namely BC, DE, and HL |
| 4 |
A Stack Pointer |
| 5 |
A Program Counter |
| 6 |
| An 8-bit flag register... |
| S | Sign Flag | 7 | If the result is positive the SF=0 else SF=1 |
| Z | Zero Flag | 6 | if the result is Zero then ZF=1 else ZF=0 |
| AC | Auxiliary Carry Flag | 4 | If carry Auxilliary Carry generated then AC=1 |
| P | Parity Flag | 2 | If the number of one bits of the result is even then PF=1 else PF=0 |
| C | Carry Flag | 0 | If the operation resulted in a carry then CF=1 else CF=0 |
| X | Positions 1, 3, and 5 are reserved |
|
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