Intel 8085
| General information | |
|---|---|
| Launched | March 1976 |
| Common manufacturer(s) | |
| Performance | |
| Max. CPU clock rate | 3 MHz to 6 MHz |
| Data width | 8 bits |
| Address width | 16 bits |
| Architecture and classification | |
| Instructions | Intel 8080 |
| History | |
| Predecessor(s) | Intel 8080 |
| Successor(s) | Intel 8086 |
The Intel 8085 is an 8-bit microprocessor and successor of the Intel 8080. The final "5" in the part number indicates that it uses only a single +5V power rail. The processor itself remains binary compatible with the 8080 ISA, only adding two additional instructions.
Design
As the successor to the Intel 8080, the 8085 simplified the design to make it easier to use by removing the multiplexing of data and state signals, instead using the lower 8-bits of the address bus. Additionally, unlike it's predecessor, the 8080, the 8085 uses only a single +5V rail for power.
Registers
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 | (bit position) |
| Main registers | ||||||||||||||||
| A | Flags | Program Status Word | ||||||||||||||
| B | C | B | ||||||||||||||
| D | E | D | ||||||||||||||
| H | L | H (indirect address) | ||||||||||||||
| Index registers | ||||||||||||||||
| SP | Stack Pointer | |||||||||||||||
| Program counter | ||||||||||||||||
| PC | Program Counter | |||||||||||||||
| Status register | ||||||||||||||||
| S | Z | – | AC | – | P | – | C | Flags | ||||||||
There are seven 8-bit general registers (A, B, C, D, E, H and L) and one status register, where A is the primary 8-bit accumulator. The other six registers can be used as either individual 8-bit registers or in three 16-bit register pairs (BC, DE and HL, referred to as B, C and H in Intel documentation) depending on the particular instruction. Some instructions also enable the HL register pair to be used as a (limited) 16-bit accumulator. A pseudo-register M, which refers to the dereference memory location pointed to by HL, can be used almost anywhere other registers can be used. The 8085 has a 16-bit stack pointer (SP) to memory and a 16-bit program counter (PC).