Serial Communications Controllers; Line Drivers And Receivers - HP 27140A Hardware Reference Manual

Serial Communications
Controllers
Line Drivers and Receivers
3-6 Functional Description
The Serial Communication Controllers (SCC) do the data format conver-
sions for data going to or coming from peripherals. The
sces
also
monitor most of the modem control lines. A Counter-Timer Parallel 110
controller associated with the
sces
controls the SR and DM modem con-
trol signals of the RS-132 ports. The Z-SO controls and monitors the SCC
via the Z-SO to SCC command interface.
The line drivers and receivers convert signals being sent at one voltage-
level to another. Since peripherals require signals at higher voltages and
different polarities than the computer, these components are required to
complete the interface.