Lake Shore Model 218 Temperature Monitor User’s Manual
Remote Operation
6-3
Bus Control Commands (Continued)
Finally, Addressed Bus Control Commands are Multiline commands that must include the Model
218 listen address before the instrument responds. Only the addressed device responds to these
commands. The Model 218 recognizes three of the Addressed Bus Control Commands:
SDC (Selective Device Clear)
– The SDC command performs essentially the same function as the
DCL command except that only the addressed device responds.
GTL (Go To Local)
– The GTL command is used to remove instruments from the remote mode.
With some instruments, GTL also unlocks front panel controls if they were previously locked out
with the LLO command.
SPE (Serial Poll Enable)
and
SPD (Serial Poll Disable)
– Serial polling accesses the Service
Request Status Byte Register. This status register contains important operational information from
the unit requesting service. The SPD command ends the polling sequence.
6.1.2.2 Common
Commands
Common Commands are addressed commands which create commonalty between instruments on
the bus. All instruments that comply with the IEEE-488 1987 standard share these commands and
their format. Common commands all begin with an asterisk. They generally relate to “bus” and
“instrument” status and identification. Common query commands end with a question mark (?).
Model 218 common commands are detailed in Paragraph 6.3 and summarized in Table 6-5.
6.1.2.3
Interface and Device Specific Commands
Device specific commands are addressed commands. The Model 218 supports a variety of device
specific commands to program instruments remotely from a digital computer and to transfer
measurements to the computer. Most device specific commands perform functions also performed
from the front panel. Model 218 device specific commands are detailed in Paragraphs 6.3.2 through
6.3.4 and summarized in Table 6-5.
6.1.3 Status
Registers
There are two status registers: the Status Byte Register described in Paragraph 6.1.3.1, and the
Standard Event Status Register in Paragraph 6.1.3.2.
6.1.3.1
Status Byte Register and Service Request Enable Register
The Status Byte Register is a single byte of data containing six bits of information about Model 218
status.
STATUS BYTE REGISTER FORMAT
Bit
–
7 6 5 4 3 2 1 0
Weighting
–
128
64 32 16 8 4 2 1
Bit Name – DLOG
Done
SRQ ESB Error Alarm
OVLD Not
Used
New
RDG
If the Service Request is enabled, any of these bits being set will cause the Model 218 to pull the
SRQ management low to signal the BUS CONTROLLER. These bits are reset to zero upon a serial
poll of the Status Byte Register. These reports can be inhibited by turning their corresponding bits
in the Service Request Enable Register to off.
The Service Request Enable Register allows the user to inhibit or enable any of the status reports
in the Status Byte Register. The
Q
SRE command is used to set the bits. If a bit in the Service
Request Enable Register is set (1), then that function is enabled. Refer to the
Q
SRE command
discussion.
Data Log Done, Bit (7)
– This bit is set when data log is completed.
