Texas Instruments 880 - Serial Interface; Seven-Bit Serial Data Structure; Eight-Bit Serial Data Structure

7.2 SERIAL INTERFACE
The serial link is made through the 25-pin con-
nector socket at the rear
of the printer. The serial
link
is asynchronous and operates in a modem
mode
or one of two direct-connect modes as
determined by configuration parameters 13, 14,
and 15.
7.2.1 Data Structu re
A received character includes 1 start
bit, 7 or 8
data bits, 1 or no parity
bit, and at least 1 stop bit
for all reception rates. Determine the data and par-
ity bits by
selecting the appropriate configuration
code from
Table 3-1. Figures 7-1 and 7-2 show
7- and 8-bit data structures.
7.2.2 Serial Connector Pin listing
The pin numbers for the serial interface are shown
in
Table 7-3.
~ START BIT
~ 8 BITS
+v
7.3 PARALLEL INTERFACE
The parallel interface can be used in either the
STROBEl ACK/BUSY protocol or the DEMANDI
STROBE protocol. The parallel connection allows
the printer to receive data, but not to send data.
7.3.1 Parallel Connector Pin listing
The parallel interface connector is a 36-pin con-
nector. The
parallel connector socket is the upper
of the two connectors on the rear of the printer.
The pin numbers
for the parallel interface are
shown in
Table 7-4.
I'"
1 STOP BIT
,--- -- -----------,
112345678
SPACE-BINARY 0
-v
+v
-v
L _______________ ---:.1 __
MARK-BINARY 1
LSB MSB PARITY
MSB-IF
PARAMETER
39 ENABLED
2222627-30
Figure 7-1. Seven-Bit Serial Data Structure
START BIT
9 BITS
/4If
1 STOP BIT
SPACE-BINARY
0
L
------------------L
123456789
----------- -- .... -----
MARK-BINARY 1
LSB MSB PARITY
2222627-31
Figure 7-2. Eight-Bit Serial Data Structure
7-3