Input Output mapped Input Output:
this method input output device is treated as I/O device and memory as
Input Output device consists of eight address lines.
eight address lines are used to interface in order to generate the address for
the input output ports, so that you can interface up to 256 inputs and 256
outputs with the microprocessor.
all know that 8085 microprocessor consists 16 bits, so you can either use lower
order address line that is A0 to A7 or higher order address lines that is
from A8 to A 15 to address input output devices where the address available
on A0 to A7 will be copied on the address lines A8 to A15.
input output mapped input output, the complete 64 K bytes of memory can be
All address lines of 64 k bytes of memory can be interfaced to memory
locations as the address space is not sharing among I/O devices and memory
and 256 input and /or output devices.
accessing I/O devices and memory separate control signals are used. For input
output port, ior bar, iow bar used. Similarly for accessing memory MEMR bar,
MEMW bar are used. By doing this way memory locations are protected from the
input and output accesses.
addresses of the I/O devices are as same as that of memory that is 16 bit for
8085 microprocessor, that why I/O devices are treated as memory and memory as
address space of memory that is 64k bytes are shared to I/O devices and
you can use all the address lines that are from A0 to A15 to memory location
as well as I/O devices.
accesses memory device and I/O device, the control signals that are MEMR bar
and MEMW bar are used so you can transfer between any register of the
microprocessor and I/O or memory devices.
input and output devices and memory devices configurations is very
complicated and expensive because more hardware is required for address
64k input /output ports or memory locations only can be accessed by the 8085
microprocessor. Therefore, the total numbers of the memory locations and i/o
ports should not be greater than 64k.