Texas Instruments 880 - Page 70

Table 7-4. Parallel Interface Signals (concluded)
Signal
Pin
32
33
34
35
36
P = Printer
H = Host
Return
Pin Source
P
SIGNAL
GROUND
HIP
HIP
*P
Signal
Description
FAULT - Goes low to indicate carriage jam or
paper-out condition.
IIF VERIFY IN
To verify proper cable connection (con-
nected to pin 35).
IIF VERIFY OUT
To verify proper cable connection (con-
nected to pin 34).
DEMAND
Inverse of BUSY. Set to a Vdc by host
(SELECT IN - ) to print.
* Motherboard jumper
E16-E17 must be installed for this signal to be active.
The
parallel interface uses TTL voltages on inputs
and outputs. Figure
7-3 shows electrical charac-
teristics.
7.3.2 Parallel Data Timing
Figure 7-4 shows the timing of typical parallel
data communication.
Figure 7-5 shows the on line and off line timing of
a Model 880 Printer with parallel interface.
7.3.3 Paper-Out and Mechanism Faults
FAULT - and PE are status lines which can be set
at any time relative to the input signals. FAULT-
is set low to indicate carriage fault or paper out;
FAULT - is set high to indicate that the faults are
repaired.
PE is set high to indicate paper out; PE is
set
low to indicate that paper has been loaded
again, and the Reset key has been pressed to
clear the error.
7-6
After either FAULT - or PE is set to indicate a
fault, BUSY is set high (DEMAND is set low). If a
STROBE- occurs while BUSY is high (DEMAND
is low), the character is held in the interface and is
not printed, and ACK - is not sent until the fault is
cleared.
7.3.4 Sequence to Initialize the Printer
The sequence to initialize the printer is a power-
up reset generated by the host system. As
shown in Figure 7-6, when the INIT - line is
pulsed low, the printer stops what it is doing,
takes itself off line (SLCT low) if it was on line,
and runs through the power-up routines. At the
end of the power-up routines, the printer goes
on line (SLCT high) if configuration code 9B is
setON.