User`s guide

‘Ihble A-l. Status Byte Definition
Bit
1 (LSB) Unused
Message
Display Message
1
2
3
!
4
5
6
7
Unit Key Pressed
End of sweep
Hardware broken
Command complete
Illegal spectrum analyzer command
Universal HP-IB service request HP-IB RQS bit
Unused
SRQ 102
SRQ 104
SRQ 110
SRQ 120
SRQ 140
The display message is an octal number based on the binary value of the status byte. This
octal number always begins with a “1” since this is translated from bit 6, the universal service
request bit. The status byte for an illegal spectrum analyzer command (SRQ 140) is as follows:
bit number 7 6
status byte 0 1
543 210
100 0 0 0
This displays the octal equivalent of the status byte binary number: SRQ 140
The octal equivalent is based on the whole binary number:
01100000 (binary) = 140 (octal) One simple way to determine the octal equivalent of the binary
number is to partition the binary number three bits at a time from the least significant bit, and
treat each part as a single binary nu
n
lber:
binary 0 1
100
000
octal
1 4 0
The decimal equivalent of the octal number is determined as follows:
140 (octal) = 1 x (8) + 4 x (8) + 0 x (8) = 96 (decimal)
More than one service request can be sent at the same time. For example, if an illegal spectrum
analyzer command (SRQ 140) and the end of a sweep (SRQ 104) occurred at the same time,
SRQ 144 appears on the spectrum analyzer display, because both bit 5 and bit 2 are set as
shown below:
bit number
7 6
543
2 10
status byte
0 1
100
100
octal value
1
4
4
=
SRQ 144
Service Request Activating Commands
With the exceptions of SRQ 140 and SRQ 110, service requests can only be activated from a
computer. (SRQ 140 and SRQ 110 are always activated.) Your programmer’s guide describes
service request activating commands under RQS and SRQ.
A-2 SRQ