Interfacing Of 8259A With 8085
Interfacing Of 8259 With 8085 Microprocessor
The interfacing steps are explained below:
- The address decoder output is connected with the CS input of the IC.
- A0 line is used to select one of the two internal addresses in the device. This is connected to A0 of the address lines of the microprocessor.
- As the device operates in I/O mapped I/O mode, the RD and WR signals are connected to IOR and IOW signals respectively.
- The interrupt INT pin of 8259 is connected to the INTR input of the 8085 microprocessor.
- INTA output of the processor is connected to the INTA input.
- When SP / EN pin is high, only one IC is used in the microprocessor-based system. If more than one IC are connected in cascade, this pin must be low.
- CAS0, CAS1 and CAS2 lines are generally opened.
- There are eight IR input lines (IR0âIR7) are available. When the IR inputs are not used, they must be grounded properly to avoid noise pulse in interrupt lines.