Features

Features

The 8085 as designed was upward-compatible in instruction set to the 8080, but had extensions to support new hardware (principally the RST n.5 interrupts as well as integration and electrical enhacements) and to provide more efficient code. The hardware support changes were announced and supported, but the software upgrades were not supported by the assembler, user manual or any other means. At times it was claimed they were not tested when that was false.

The 8085 can accommodate slower memories through externally generated Wait states (pin 35, READY), and also has provisions for Direct Memory Access (DMA) using HOLD and HLDA signals (pins 39 and 38). An improvement over the 8080 is that the 8085 can itself drive a piezoelectric crystal directly connected to it, and a built in clock generator generates the internal high amplitude two-phase clock signals at half the crystal frequency (a 6.14 MHz crystal would yield a 3.07 MHz clock for instance).