Keithley 2182, User Manual, Page: 300 / 339

F-8 IEEE-488 Bus Overview
ATN (Attention) — The controller sends ATN while transmitting addresses or multiline
commands.
SRQ (Service Request) — SRQ is asserted by a device when it requires service from a
controller.
Universal multiline commands
Universal commands are those multiline commands that require no addressing. All devices
equipped to implement such commands will do so simultaneously when the commands are
transmitted. As with all multiline commands, these commands are transmitted with ATN true.
LLO (Local Lockout) — LLO is sent to the instrument to lock out the LOCAL key and all
their front panel controls.
DCL (Device Clear) — DCL is used to return instruments to some default state. Instruments
usually return to their power-up conditions.
SPE (Serial Poll Enable) — SPE is the first step in the serial polling sequence which is used
to determine which device has requested service.
SPD (Serial Poll Disable) — SPD is used by the controller to remove all devices on the bus
from the serial poll mode and is generally the last command in the serial polling sequence.
D
7
D
6
D
5
D
4
X 0 0 0
Command
X 0 0 1
Command
X 0 1 0
Primary
Address
X 0 1 1
Primary
Address
X 1 0 0
Primary
Address
X 1 0 1
Primary
Address
X 1 1 0
X 1 1 1
Bits
D
3
↓
D
2
↓
D
1
↓
D
0
↓
Column
→
Row
↓
0 (A)
0 (B)
1 (A)
1 (B)
2 (A)
2 (B)
3 (A)
3(B)
4 (A)
4 (B)
5 (A)
5 (B)
6 (A)
6 (B)
7 (A)
7 (B)
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
0 1 2 3 4 5 6 7 8 9
10
11
12 13 14 15
NUL SOH
STX ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR
SO
SI
GTL
SDC
PPC*
GET
TCT*
DLE
DC1 DC2 DC3 DC4 NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS
US
LLO DCL
PPU*
SPE
SPD
SP
!
“ # $
%
&
‘ ( )
• +
, - . /
0 1 2 3 4 5 6 7 8 9
10 11 12 13 14 15
0 1 2 3 4 5 6 7 8 9
: ;
< = >
?
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
UNL
@
A B C
D
E F
G H
I J
K
L
M N O
0 1 2 3 4 5 6 7 8 9
10
11
12 13 14 15
P
Q
R S T
U V
W
X Y Z
[
\
]
∩

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
UNT
a b c d e
f
g h
i j
k
l
m
n o
p q
r
s
t
u v
w
x y z
{ : }
≅
DEL
ADDRESSED COMMAND
GROUP
(ACG)
UNIVERSAL
COMMAND
GROUP
(UCG)
LISTEN
ADDRESS
GROUP
(LAG)
TALK
ADDRESS
GROUP
(T
AG)
PRIMAR
Y
COMMAND
GROUP
(PCG)
SECONDAR
Y
COMMAND
GROUP
(SDC)
*PPC (P
ARALLEL
POLL
CONFIGURE) PPU (P
ARALLEL
POLL
UNCONFIGURE),
and TCT (T
AKE CONTROL) not implemented by Model 2182.
Note: D
0
= DIO1 ... D
7
= DIO8; X = Don’
t Care.
Figure F-3
Command
codes