Figure 7-6.—IOA/IOC interface.
(fig. 7-6). Some of the data and control signals
the pcb to match the electrical interface of the
exchanged between the IOC and IOA include:
Buffer enables
Acknowledge enables
Set/clear output register
Data bits
Request lines
Input/output available
I/O Pcb(s)
In the I/O pcb arrangement, minis and micros
have multiple I/O pcb’s or a single I/O pcb. When
multiple I/O pcb’s are used, each I/O pcb will be
assigned a number of external equipments for I/O
operations. In this arrangement other circuitry will be
used that basically performs the same duties as a
controller. In the single I/O pcb arrangement, the
functions that an IOA would perform are contained on
external device(s) to that of the computer. The
connectors for the input and output channels/ports are
usually located on the rear of the I/O pcb (fig. 7-7).
Figure 7-7.—Connector parts on the rear of a microcomputer.
7-7
