Tektronix 2221 - RS-232-C Parameter Selection

Options and
Accessories --
2221
Operators
NOTE
Do not hook up external devices to both the DTE
connector and the
DCE
connector at the
same
time .
error . If OPC
is also on ,
additional
system
events (
i.e. ,
warnings and operation complete ) will also generate an
asynchronous service request . All status bytes are
prevented from reporting if RQS is off , but the SRQ
indicator does not
indicate that a
status byte is
pend
ing . In this case , the event code must be queried
( EVEnt ? ) to find out if an event has happened .
RS - 232 - C
DCE
Connector -
Provides
a
connector
that
meets the EIA RS - 232-2 standard for data communica
tions equipment ( see Figure 7-3 ) . Table 7-10 lists the
function of each pin of the connector . The connector is
provided only on Option 12 instruments .
u
The ADDR indicator is on when a carrier is detected .
With no
devices
connected to
either
the
DTE
port or
the DCE port , the ADDR indicator will be on . If an
RS - 232 - C
DCE
device
is
connected to the
DCE port ,
the carrier will also be on all the time . The indicator will
be off if a
DTE
device
is
connected to the
DTE
port
and no carrier
is
detected
.
Option 12 Intertace Status Indicators
u
The three
indicator labels ( SRQ ,
ADDR , and
PLOT )
above the
CRT
indicate the status of
the
Communications
interface .
Refer to
Figure 7-2 (
shown
previously
)
for the
location of the
status
indicators .
Their
operation is
as
follows :
The PLOT
indicator
is
on when the
communication
option is currently sending waveform data . Acquisitions
are inhibited during this time .
RS - 232 - C Parameter Selection
The
SRQ indicator is
on
only
during the
time an
asyn
chronous
status
byte
is being
sent . A
status byte or
event
code is not
generated
for
power - on .
Events
must be queried to receive pending events codes .
Status must also be
queried
to
receive
pending status
bytes , except for command and execution error status
which are
returned
immediately
upon
recognition of an
Selection of RS - 232 -
C
parameters ( baud
rate , parity ,
and line
terminator
)
must be
made prior to
power on
using
the RS - 232 - C PARAMETER switch and Table 7-11
through Table 7-13 . Changes to the PARAMETER switch
after power on
will not be
read until the
next power on
occurs . PARAMETERS switch settings and setups for
some common printers and plotters are given in Appendix
B. There are two other communications parameters that
are set using commands via the interface itself . These are
STOP
bits
and
FLOW control . The
most used
setting
for
STOP is 1. The power - on default for FLOW is OFF .
u
uu
Table
7-10
RS - 232 - C DCE
Connector
Signal
Name
Pin
Function
Internal
External
1 1
Chassis
ground
CHAS
GND
CHAS
GND
Baud Rate .
Baud rate
switch
settings
determine the
baud rate
used by the
instrument for both
sending
and
receiving data . The available baud rates are listed in
Table 7-12 .
2a
IRXD
TXD
Transmitted
data
3a
ITXD
RXC
Received
data
4
ICTS
RTS
Request
to
send
u
When
OFF
LINE
(
baud
- rate
switch
settings
1111
)
is
selected , the instrument still presents an active load to the
other RS - 232 - C
device , but it
can't
send
or
receive any
interface traffic .
5
IRTS
CTS
Clear to
send
6
IDTR
DSR
Data
set
ready
7a
SIG
Signal
ground
SIG
GND
GND
Use Table 7-11 , Table 7-12 , and the PARAMETERS
switch
to
select
the
desired baud rate .
8
IRLSDC1 RLSD
Received line
signal
detect
20
IDSR DTR
Data
terminal
ready
* These lines
are all
that are
required for
communication
without hard
control lines .
Parity . The
selected parity setting
determine the
oscilloscope's response to received parity errors and the
parity of data sent by the oscilloscope .
7-12
U