*** Welcome to piglix ***

8085

Intel 8085
KL Intel P8085AH.jpg
An Intel 8085AH processor.
Produced From 1975 to 1990s
Common manufacturer(s)
  • Intel and several others
Max. CPU clock rate 3, 5 and 6 MHz
Min. feature size μm
Instruction set 80
Transistors 6,500
Predecessor Intel 8080
Successor Intel 8086
Package(s)
Intel 8085 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 - CY Flags

The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor produced by Intel and introduced in 1976. It is a software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added interrupt and serial input/output features. However, it requires less support circuitry, allowing simpler and less expensive microcomputer systems to be built.

The "5" in the part number highlighted the fact that the 8085 uses a single +5-volt (V) power supply by using depletion-mode transistors, rather than requiring the +5 V, −5 V and +12 V supplies needed by the 8080. This capability matched that of the competing Z80, a popular 8080-derived CPU introduced the year before. These processors could be used in computers running the CP/M operating system.

The 8085 is supplied in a 40-pin DIP package. To maximise the functions on the available pins, the 8085 uses a multiplexed address/data bus. However, an 8085 circuit requires an 8-bit address latch, so Intel manufactured several support chips with an address latch built in. These include the 8755, with an address latch, 2 KB of EPROM and 16 I/O pins, and the 8155 with 256 bytes of RAM, 22 I/O pins and a 14-bit programmable timer/counter. The multiplexed address/data bus reduced the number of PCB tracks between the 8085 and such memory and I/O chips.

Both the 8080 and the 8085 were eclipsed by the Zilog Z80 for desktop computers, which took over most of the CP/M computer market, as well as a share of the booming home-computer market in the early-to-mid-1980s.

The 8085 had a long life as a controller, no doubt thanks to its built-in serial I/O and 5 prioritized interrupts, arguably microcontroller-like features that the Z80 CPU did not have. Once designed into such products as the DECtape II controller and the VT102 video terminal in the late 1970s, the 8085 served for new production throughout the lifetime of those products. This was typically longer than the product life of desktop computers.


...
Wikipedia

...