Interface Basic Programming Statements; Buserror; Basic Statements Necessary To Send Bus Commands - Keithley 595 Instruction Manual

From the preceding discussion, the message is clear: make
4.7 FRONT PANEL ASPECK OF IEEE-488
sure the proper softyare is being used with the interface.
~OPERATION
Often, the user may iucorrectly suspect that the hardware
is causing a problem when it was the software all along.
The Model 595 has a number of front panel messages,
associated with IEEE-488 programming. These messages,
4.6.2 Interface BASIC Programming Statements
which are intended to inform you of certain conditions that
occur when sending device-dependent commands to the
instrument, are listed in Table 4-4 and are described in the
The programmin g instructions covered in this section use
examples written with Hewlett Packard Model 85 BASIC.
following paragraphs.
This computer was chosen for these examples because of
its versatility in controlling the IEEE-488 bus. This section
covers those HP-85 statements that are essential to Model
Table 4-4. IEEE-488 Front Panel Messages
595 operation.
Message ( Description
A partial list of ~Hp-85 statements is shown in Table 4-3.
W-85 statements have a one or three digit argument that
:tzz
"Bus error" no &note, IDDCJDDCO
must be specified as part of the statement. The first-digit
rpA--- Overrun
is the controller interface select code, which is set to 7 at
"m !r (A, H, L, V) or Conflict (Q C)
the factory. The last two digits of those statements, requir-
"tiGr
Waiting
for trigger
ing a 3-digit argument, specify the primary address.
Blank Digits Triggered; reading will be displayed
after the measurement conversion.
Table 4-3. BASIC Statements Necessary to Send
Bus Commands
Another front panel aspect of bus operation is that the front
panel controls are functional unless the LLO~(l0cz.J lockout)
command was asserted. See paragraph 4.8.3 for more in-
,formation on LLO.
Action
( HP-85 Statement
Transmit shing to device 28.
Obtain string from device 28.
~ Send GTL to device 28.
Send SDC to device 28.
Send DCL to all devices.
Send Remote Enable.
Cancel Remote Enable.
Serial poll device 28.
Send Local Lockout.
~ Send GET to device.
Send IFC
CLEAR 72s
CLEAR 7
REMOTE 7
LOCAL
i
SPOLL C728)
LOCAL LOCKOUT
TRIGGER728
I
RBORTIO 7
I
bErr
4.7.1 Bus Errors
A bus error wiU occur if the instrument receives a device
dependent cornman d when it is not in remote, or if an il-
legal device-dependent command (IDDC) or illegal device-
dependent command option @DCO) is sent to the instru-
ment. Under these conditions, the complete command
string will be rejected and the following bus error message
will be displayed:
Those statements with a 3-digit vent listed in the tabIe
show a primary address of 28 (the factory default primary
The LJI error status word must be read to determine the
address of the Model 595). For a different address, you
nature of the bus error (see paragraph 4.9.23). Also, the in-
would, of course, change the last two digits to the required
stzument can be programmed to generate an SRQ under
value. For example, to send a GTL command to a device
these conditions (see paragraph 4.920).
using a primary address of 22, the following statement
would be used: LOCAL 722.
A no remote error can occur when a comman d is sent to
the instrument when the REN line is false. Note that the
C^__^ _<il^ ^Ll_-_-r_L _.._ -..- L..-_. _- -.._- ---c-___
state of RFN is only tested when the X character is received.
5oIl1'2 "I ULtc sid~emmw 1,avr TW" 1unn.s; me czxiiu c"mlgura-
tion depends on the command to be sent ~----~l-- L---
~~-~&I IDDC error-can occur when an illegal Device-
-pie, CLEAR 7 sends a DCL commar
on the bus, while CLEAR 728 sends the
to a device with a prima
' ' ' ^^
[vdr;~~d~$.~
Dependent Co mmand such as EIX is received bj the Model
SDC command
595 (this command is invalid because the instrument has
ry aoaress or a.
no command assc+at$d with that letter). ~Similarly, an
IDDCO error occurs when an Illegal Device-Dependent
4-6