Table of Contents
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Table 21-1.
IEEE-488 Interface Controllable Functions
Control/Measurement
Comment
Control/Measurement
Comment
Function Swilch
Generate/Power Monitor/
Monitor
Modulation Control
ContinuousrQFF.tBURST
WldcbandfNarrowband Swilch
Image High/Low Swilch
"' " """")
PL Frequency
Frequency en:ry lobe
OPL Code
supplied by pronrarn
F1equenc1es not avmlable
Tone A Frequency
from memory :able
Tone B Frequency
Duplex Oscl11alor Swilch
0-10 MHz/OFF/45 MHz
Time Sequence Se!ecl
Sequences 1 !hrough
5
only
(Note
2l
Keyboard
NtJmenc Entries 0-9
Can be
uansmi\h~d
to H1e
Wallmeler Element Select
bus
External Modulation
Modulat11:>n sellable to any
Display Mode
Generate/Monitor
measurable level
Metenng
(Note
1)
Code Synlhesizer Modulation
10-20 KHz De;11&l10n
1n
Hl Hz
Modulation
steps)
;Note
31
Spectrum Analyzer
\0·90(\~
AM 1n 0.
B~
steps)
Duplex Genera10r
RF Memory
Tone Memory
Frequem::y Coun1er
DVM
RF level
RF level sellable to any
dlsplayab1e level i-140 \o
·11 -d8rn
m
0.1 oBm steps
!Note
3) (Note
,,
EJ~temaJ
Wattmeter
Ol!set Osci!!ator Adjust
O!Jptex Generator Frequency
IF
Sellable from fo to
to
~
10
Scope AC
MHZ Hl 1 KHz steps \Sw11ch)
Scope DC
placed 1n 0-10 MHz: pos1tion)
Remote Termmai f·.-lor!<;
{Note
J)
Un1! can also d1splay
il
subset
Scope Vertical Step Allenuator
0 01' (}
1_
1 10
volts
of
ASCII
ctl<Hac:ers l.numera1s
0-9.
upper case
<Jlpha leHers
/i·Z. plus other
symbols~
ASCI!
ch;u,1cters 20 lhru 5F Hexa-
Horizontal Scope Sweep
1
' "
100 rn11!1Secor.(lS
1 \D. 100 mtcroseconds
ExWrnal
dec1ma!) enables display ot
Input Power Meier
operator messages on
ern
Frequency Error
d!Splay in a transparent ter-
Deviation • or
~
minal mode
~-o
AM · or-
Function Mode
FM
jNote
I}
cw
AM
SIN AD
Reading returned as
d1sp1aved on screen (N(fle
31
External DVM {AC or DC}
SSB,.DSB
External Frequency Count
SWP 1-10 MHz
External Power Meter FWD/REV
SWPO!Ji-1 MH:
Code Synthesizer Mode
PL.·OPL
No!ns
11)
M,<y
tH~
attested b·r
r:>the: contmls
(see below)
PL:OPL
lnv~:!rl
(2)
Sequence
5 lltnlng
IS
progr.ammatllf:-
under
IEEE 1Jus control
Tone A
(3)
lis rea<J1ng <S d!Spii'lyB.<J.
LED conespomlmqlo nppropnate
Tone 8
:l•sPi<l'{ awl
~Lmctmn
mode
wdl
Jilt;mm<~!e
AiB
(~)
nw
IEEE-Gus opt;on. due to 11
ch<~nge
in
the
RF ;;tep
attenuator
Tone Remote
rr:"~ltic::;.tlW
rnaxirnwn HF output
:0
•11 d8m
NON-CONTROLLABLE FUNCTIONS
Since control and monitor functions of the inter-
face are implemented to obtain remote measure-
ment capability. certain front panel controls are
not implemented in the interface due to their
local operator orientation. A list of these oper-
ator oriented controls are as follows:
Power On/Off
Power Mode Indicators
Display Focus
Display lntenslty
Dispersion/Sweep
Scope/DVM Vertical Vernier
Scope Trigger Level
Scope Trigger Slope
3cope Horizontal Sweep Vernier
Scope Vertical Position
Scope Horizontal Position
Receiver Squelch
Receiver Volume
Zero
Beat Indicator
RF Scan
RF Memory Table
Tone Sequences, 6. 7. and 8
Entries
21-2
Deviation Limit
Battery Voltage Reading
Deviation Limit Alarm (Disabled
Under Remote Control)
Attenuator
0 Indicator
Battery Below Limit Warning
BFO Frequency Adjust
21-7. IEEE-488 BUS STRUCTURE
21-8. The following discussion briefly describes the 488 Bus operation. It is not a complete definition of the
total bus structure or capability. For complete information a copy of IEEE Standard 488 should be obtained.
21-9. Bus Signals. The IEEE-488 Bus consists of 16 parallel lines. The lines are divided Into three groups.
Lines DI01-DI08, Data Input Output, form the 8-bit data bus for the bidirectional transfer of control and ASCII
characters. Three handshake lines, Data Valid (DAV), Not Ready for Data (NRFD), and Not Data Accepted
(NDAC), control the transfer of data on the data bus. The remaining five lines can be termed the bus
management lines with functions as follows:
Attention (ATN)
Interface Clear (IFC)
Service Request (SRQ)
Remote Enable (REN)
End or lndentify (EOI)
- When true the data bus carries an address or
a comand when false it carries data.
- When true all devices on the bus are placed
in a known quiescent state.
-
Indicates a device on the bus needs service.
-
Enables the remote control feature of the devices on the bus.
-
Indicates the end of a multiple byte transfire.
21-10.
Data Transfer.
Each byte of data that is transferred across the data bus is synchronized with a
handshaking procedure. This· procedure allows devices with different data transfer rates to share the same
bus. The handshake cycle starts when the source device which has data to transfer checks for a false condition
on the NRFD line. When NRFD is false, all devices on the bus are ready to accept data. The source then puts the
data onto the data bus and sets the DAV to its true state. The acceptor devices input the data, set the NRFD line
to its true state, and when ready sets the NDAC line to its false state. Because the NRFD and NDAC lines are
wire-ORed the line will not go to the false state until all devices on the bus have released the line. Thus the
slowest device on the bus determines the transfer rate. When the NDAC line goes false the source devices sets
the DAV false which in turn causes the acceptor devices to set the NDAC line true. When the acceptor devices
have completed processing the data byte just received they allow the NRFD line to go to the false state
completing the handshake. As the data transfer continues the cycle repeats for each data byte.
21-11.
Bus Address.
Each device on the bus is assigned a four bit address by the programer. The address
assigned to the device is set by an address switch within the device. On the analyzer the address switch is on
the IEEE Interface Module. Only the top four switches are used to set the address. The fifth switch is unused.
To set the address use the binary equivalent of the address number and set the switches to the ON position for
a logic 1. The least significant bit is the top switch.
21-12.
Programming
21-13.
Programing the system analyzer consists of first addressing the unit as a listener, transferring the
control commands to the unit, and then sending a command termination sequence. To obtain data from the
system, the pertinent control commands are first transferred to the unit and then the unit is addressed as a
talker. As a talker the system outputs onto the bus the data requested by the control commands.
21-14. The bus controller is the central part of the automatic system. The program, consisting of sequences
of analyzer control commands and sequences of controller instructions for handling the return data, is
contained within the controller. The user must initially write the program so that the desired test sequences
and data outputs will be obtained. The following paragraphs define the instruction set and data formats that
can be used to control or will be returned from the system analyzer_The user must insure that the controller is
compatible with the IEEE-488 Standard bus and that its program is correct for the instruments on the bus.
21-3
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