Gossen MetraWatt SSP 120 Series, Operating Instructions Manual

Page: 71 / 92

GMC-I Messtechnik GmbH 71
SIG1_SIG2, SIG1_SIG2? – Analog Interface Signal Outputs
Function and manual operation:

As opposed to manual operation, the computer generated
SIG1_SIG2 command addresses both signal outputs
simultaneously.

Signal output 1 : dependent upon power output status.

Signal output 2 : dependent upon current output control mode.

The status of the SIG1_SIG2 function is not saved as a device
setting with the SAVE key.

See explanations on page 29 ff.
Programming
Setting command: SI G1_SIG2 txt1,txt2
Parameter: txt1,txt2 (selection )
Parameter type: Text (character)
Default setting: After RESET (*RST)

unchanged
Example (HP Basic):
OUTPUT 713; "SIG1_SIG2 OUT, MODE"
Query
Displays the selected function for the signal outputs at the analog
interface.
Programming
Query command: SI G1_SIG2 ?
Response string: SIG1_SIG2 txt1,txt2
Length: 19 characters, fixed
Parameter: txt1, txt2 (selection)
Example (HP Basic):
OUTPUT 713; "SIG1_SIG2?"
ENTER 713; A$
DISP A$

Display: SIG1_SIG2 OUT,MODE
SRQ – SERVICE REQUEST
Functions

The service request SRQ is only available via the IEEE parallel
interface.

SRQ can be activated by any device which is connected to the
IEC bus.

SRQ is the only way for a device to trigger a specified action at the
controller.

The SRQ lead is activated by the KONSTANTER when it requests
service from the controller .

SRQ allows for simultaneous execution of several tasks by the
controller , and thus increases its efficiency .

The controller can execute other tasks until it receives an SRQ
from the device .

In response to the SRQ message via the IEC bus, the control
computer can start serial polling of the device status ( serial
poll ).

In this way, the device which transmitted the SRQ as well as the
reason for the message, are both determined.

If only one device is connected to the IEC bus , the controller can
read out the status byte directly and trigger the desired function
after receiving an SRQ.

Primarily, the controller should read out information regarding
device statuses and events.

The service request is transmitted via the common interrupt lead
(SRQ) at the IEC bus.

SRQ trigger conditions can be selected from any of the messages
which occur in the event registers (including MAV) .

Which event message or messages result in an SRQ message
is determined by
setting the enable registers accordingly ( SRQ
masking ).

If all utilized devices with SRQ capability are equipped with
parallel polling as well, it may be possible to identify the device
which generated the SRQ message more quickly by means of
this function, assuming they have been configured accordingly.
Example: SRQ triggering upon receipt of an incorrect command:

Assuming all event registers have an initial value of 0.

An incorrect command is received.

The ESR (event standard register) sets bit 4 ( EXE , execution
error) or bit 5 ( CME , command error).

Did you previously set bits 4 and 5 in the ESE enable register
(command: *ESE 48 )?

If so, the ESR group message is generated in the STB (status
byte register).

The associated SRE enable register must be set to bit 5
(command: *SRE 32 ).

The ESR bit is now able to generate the MSS group message
(master summary status).

The MSS group message enters itself once again to bit 6 in the
STB (status byte).

In this way, a signal is generated indicating that there is at least
one reason for generating an SRQ message.

The SRQ message is then triggered by the downstream service
request function .

The respective commands for setting the assumed SRQ
conditions are thus: *ESE 48; *SRE 32 .

Service calls from the ERA and ERB event registers, or from the
MAV message, are generated in the same way.
Setting range: OFF
ON
SIG n Passive high
Active low
OUT OUTPUT ON
OUTPUT OFF
Passive high
Active low
MODE OFF or CV
CC or OL
Passive high
Active low
SEQ GO Active low
SSET OFF
ON
Passive high
Active low
U_LO U
meas

U
min
U
meas

U
min
Passive high
Active low
U_HI U
meas

U
max
U
meas

U
max
Passive high
Active low
I_LO I
meas

I
min
I
meas

I
min
Passive high
Active low
I_HI I
meas

I
max
I
meas

I
max
Passive high
Active low