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CPU
4.3.
parallel I/O Ports
Zilog
CPU
The Z80B PIO (U94) uses ports A and 8
for
interfacing
the
line
printer
(Centronics
or
Data Products) to the System
8000. At Port A, bidirectional buffer
(UI03)
supplies
the
printer control output and printer status input
lines~
Port
8 is the printer data output port(BO-B7) •
From Port B, the data bits
(BO
through
B7)
are
buffered
(U108)
and
output
as
data
bits
(Data 0 through Data 7)
through the P2/J2l I/O connector to the printer connector on
the
back
panel.
Figure 4-3 shows the parallel I/O circuit
printer interface.
+5V
ItDIfIECT10NAL
ItIO
R1.
FROM
TO SECOHQARY
IlUFnR
1K
1K
u.
+5V SBlAL IJOARD
U103
DATA ST"OafIDATA STROIlE-
L
O--""----I.~I
INPUT PRIME·
P2.12C} "'INTER
1
-+~ON~U~NEI;.:SE==::L::;:;Eer=--
_ _
--e
~:~~
CONTf'OL
~
..-+--'
I
----DA
. .
T--:--:...~OIF=;~=L=T-NO-WL.E-DG-E-.
--e
P2-2QC
PRINTER
ill
'*
1---+-------. . . . "
I
=~====~
....
P2-1tIC
STATUS
I------t---!~-~-..-.------
.....
P2.17C
P2.1C
UNf:
THROUGH
PRINTER
P2-1OC
+5V
CLOCK I
t
VI
TO CPU
III FROM
SIOI3
LAD 2
LAD 1
Figure 4-3
Parallel I/O (Sheet 7)
4.3.1.
printer
Control
Outputs:
The
parallel
printer
interface
Data
Strobe- or Data Strobe signal is configured
by jumper from either the A port AD output or the BRDY
out-
put
of
the PIO.
The jumper configuration E17 - E18 is the
Centronics/Printronix standard interface direct ,from the
AD
output.
The Elfi - E17 configuration supplies the Data products posi-
tive
Data
Strobe
signal
from
the
BRDY PIO output.
The
remaining control bits Al,A2, and A3 are not used.
Table 4-1 lists the control
sig~als
for the
two
configura-
tions.
,"
4-4
Zilog
4-4
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