Bus Commands; Uniline Commands - Keithley 705 Instruction Manual

Figure 3-3 shows the connector pin assignments. The connec-
tor contact designations are listed in Table 3-4.
CONTACT 13
CONTACT 24
CONTACT 1
CONTACT 12
Figure 3-3. Contact Assignments
Figure 3-4. Model 705 IEEE Bus Connector
2. Primary Address Selection-The primary address must be
set to the appropriate value when using the Model 705 in
the addressable mode (refer to step 3).
3. The primary address is selected by front panel program
number three. For more information concerning the primary
address selection refer to paragraph 2.6.4.
3.4 BUS COMMANDS
The Model 705 may be given a number of special bus com-
mands through the IEEE-488 interface. This section briefly
describes the purpose of the bus commands which are
grouped into the following three catagories:
1. Uniline Commands: Sent by setting the associated bus lines
low.
2. Multiline Commands: General commands are sent with the
ATN line low.
3. Device Dependent Commands: Special commands that de-
pend on device configurations; sent with ATN high.
Table 3-4. IEEE Bus Connector Contact Designations
Contact
Number
1
2
3
4
5
6
7
8
9
IO
11
12
13
14
15
16
17
18
19
20
21
22
23
24
IEEE-488
Designation
DIOI
0102
D103
D104
EOI (241,
DAV
NRFD
NDAC
IFC
SRQ
ATN
SHIELD*'
D105
D106
D107
D108
REN (24)"
Gnd, (6)"
Gnd, (7)"
Gnd, (8)"
Gnd, (9)"
Gnd, (IO)*
Gnd, (II)"
Gnd, LOGIC
Type
Data
Data
Data
Data
Management
Handshake
Handshake
Handshake
Management
Management
Management
Ground
Data
Data
Data
Data
Management
Ground
Ground
Ground
Ground
Ground
Ground
Ground
*
Numbers in parentheses refer to signal ground return of
referenced contact number. EOI and REN signal lines return
on contact 24.
**The cable shield is normally connected to contact 12. This
shield should be connected to ground only at the controller
end to avoid ground loop problems.
3.4.1 Uniline Commands
As stated previously, uniline commands are sent by setting the
associated bus line low (true). The five uniline (single line)
commands are:
1. ATN (Attention)-The ATN command is sent when the in-
formation on the data bus is a universal or addressed com-
mand. Universal and addressed commands are described in
paragraphs 3.4.2 and 3.4.3. When the ATN line is high, the
byte on the data bus is considered to be data. The Model
705 responds to the appropriate universal and addressed
commands when the ATN line is low, and to the device-
dependent commands when the ATN line is high, assuming
it is properly addressed.
2. REN (Remote Enable)-The controller sends this command
to all devices on the bus when remote operation is desired.
The Model 705 responds by setting itself up for remote
operation as indicated by the front panel REMOTE LED.
3. EOI (End Or Identify)-EOI is sent during the last byte of a
multibyte transfer by setting the EOI line low. In this way,
the last byte is identified allowing variable length data words
to be transmitted. The Model 705 implements this com-
mand when in the appropriate bus response mode, as
stated in paragraph 3.5.
3-5