Printer Interface - IBM 6400 series Maintenance Manual

to withstand an AC input overvoltage of 300 VAC for one second with no
degradation of DC output voltage or damage to printer circuits.
DC Power
The power supply board contains two DC power supply systems for the
printer. The first is a + 5 V bus for logic. The second consists of + 48 V and
+ 8.5 V buses for the hammer bank and all motors.
The + 5 V supply has an isolated return line that connects to the + 48 V
return at the printer load. Both returns are tied together in a single-point
ground. The + 5 V power supply has its own inverter, separate from the + 48
V and + 8.5 V outputs.
There is an opto-isolated input on the power supply that will shut down and
latch off the + 48 V and + 8.5 V supplies unless it is pulled up to 5V with a 1K
Ω resistor. This resistor is mounted on the controller board and may be pulled
down or disconnected by software or internal cable interlocks. The + 5 V
output will remain stable for reporting and latching the fault condition. The
return for this signal is the + 5 V return. In addition, this shutdown circuit
discharges and latches the + 48 V down to a level lower than 15 V in less
than 200 milliseconds and requires recycling of the circuit breaker (On/Off
switch) to reset the latch.
Loss of + 48 V is seen by the EC and reported as a fault.

Printer Interface

The printer interface is the point where the data line from the host computer
plugs into the printer. The printer interface processes all signals and data to
and from the host computer.
The printer supports supports a number of standard and optional interfaces
to the host:
Centronics parallel (standard)
IEEE 1284 parallel (standard)
EIA-232-E serial (standard)
EIA-422-B serial (standard)
Coaxial/twinaxial "Expansion-CT" (optional)
Ethernet10Base-2 or 10Base-T adapter (optional)
52
Principles of Operation