Interfaces8–2
Introduction
The MVP–Series printer interfaces are logically and electronically
compatible with the Centronics and Dataproducts interfaces. The Centronics
and Dataproducts interfaces allow the parallel transfer of 8 data bits, one byte
at a time. The switch from one interface to the other requires a simple change
of the printer’s input/output (I/O) cable, terminating resistors, and
Configuration Option 66 (see “Switching Interfaces” on page 8–26 ).
Centronics and Dataproducts Interface Characteristics
Centronics and Dataproducts interface circuit characteristics are as follows.
Interface Cable
The cable must not exceed 40 feet and must allow the transmission of signals
having standard TTL logic level (0.0V to +0.5V low and +2.4V to +5.25V
high). Use shielded cable with the shield grounded to minimize electrical
noise.
Logic Levels
0.0V to +0.5V low; +2.4V to +5.25V high.
Receivers
TTL 74LS14 with a 1000–ohm pull–up terminating resistor pack in location
18C (Centronics) or optional 220–ohm and 330–ohm pull–up/pull–down
terminating resistor packs in locations 18C and 17C, respectively
(Dataproducts).
Drivers
TTL 7407 with a 1000–ohm pull–up terminating resistor pack in location
15C (Centronics or Dataproducts).
Terminating Resistors
The Centronics parallel interface requires that 1000–ohm resistor packs be
installed at Parallel Controller PCBA coordinates 15C and 18C see
Figure 8–5. Typical circuits using the resistors are shown in Figure 8–6. The
Dataproducts Interface requires the 220–ohm resistor pak at coordinates 18C
and a 300–ohm pack at coordinates 17C. A 1000–ohm pack is installed at
location 15C. A resistor pack is not required with the Serial Controller
PCBA.
Logic Configuration
Standard positive true; Option Code 63 is configurable to negative true logic.