Radio Shack TRS-80 Service Manual page 55

APPENDIX A
PARALLEL INTERFACE SPECIFICATIONS
All printers contain
a
common
7-bit parallel interface.
An
optional eighth
bit
is
available, as
required by the
user.
Detailed
in-
formation describing the standard interface timing,
signal
descriptions, connectors and
other specifications are
contained
in
this
appendix.
The
intent
is
to
provide the user with the
technical
information required
to interface directly to
a
standard
printer,
or
if
necessary to design
a
special
interface to adapt the
printer
to
a
particular terminal.
INTERFACE TIMING
PARALLEL DATA.
DATA STROBE.
ACKNOWLEDGE
BUSY.
26-1150
BUSY
I.Ous
(MINI
1.0us
(MINI
1.0us
(MIN)
~500us
(MAX)
W//////////M
-ACK DELAY
(For
Normal
Data)
BUSY
DELAY
H
-BUSY-
-BUSY
DELAY
1
J
-ACK
-»|
*-ACK
DELAY
(For Busy Condition)
NORMAL
DATA
INPUT TIMING
ACK
DELAY
ACK
2.5-10
usee.
2.5-5.0 usee.
BUSY DELAY
ACK
DELAY
ACK
0-1.5
usee.
0-10
usee.
2.5-5.0 usee.
BUSY DURATION
Line
Feed
Vertical
Tab
(1-inch)
Form
Feed
(1
1 -inches)
Delete
Bell
Select*
Deselect
Print
Command
(Return time
—
no-busy)
75-105
msec.
240-270
msec.
2.07-2.11
sec.
100-400
usee.
100-400
usee.
Until printer
is
selected
16.7 msec. /character
2.4
sec.
(max.)
1.6 sec. (max.)
*No
busy,
if
inhibit
prime on
select option
is
used.
A-1