HP 1630A Operating And Programming Manual page 180

RS-232C/V .24 and RS-449
The HP 1630A/D/G and HP 1631A/D
logic analyzers have trace resource terms
that allow you to trigger on a precise
sequence of data within the serial stream.
For example, a logic analyzer with the
HP 10342B can be set up to find specific
patterns in the data stream . Here, the logic
analyzer is scanning the data stream for an
"L," which is defined as the term "a"
(figure 1). When it is found, the analyzer
stores it-, and looks to see whether the next
term is "O" or "b ." If it finds "b" next to
"a," it stores both terms and proceeds to
look for "c." If it does not find "b" next
to "a," the analyzer looks for a second "a ;"
stores it, and then looks to see whether a
"b" follows it. This process continues until
a "b" is found that follows an "a." This
ensures that the exact sequence is located.
The analyzer then finds "c," stores it, and
begins its trace upon finding "d ."
After the trace is complete, the
analyzer presents the data in an
easy-to-read inverse-assembled format .
There is no need to interpret symbols
(figure 2). The analyzer displays "a," "b,"
"c," and "d" followed by the rest of the
serial stream . You can easily identify
transmissions, receptions, their respective
input pin numbers, and the data.
To locate bottlenecks, the HP 1630G
displays the relative time between states .
Rewriting a particular section of code can
greatly reduce transmission time .
HP-IB
The HP 10342B simplifies monitoring
and locating HP-113 problems . The
HP logic analyzer's trace capability
allows you to trigger on a specific address,
data, or control function .
HP-IB is based on a three-wire
handshake process for transferring data.
The handshake process can be viewed
with the timing analyzer to ensure
proper sequencing. The display shows
that the sequence occurred properly but
that there is a glitch on the
not-ready-for-data (NRFD) line . The
HP 1631A/D's 200 megasample/second
digitizing oscilloscope capabilities can be
used to display the glitch with up to
5-ns resolution (figure 3).
State Llsting ___------------------ -------------------__------
L
41Y
ab :U TX RX PIN
BATH . HER ITS CIS OTR DSR. CD TL~e
Base ,
l
Figure 1 - The logic analyzer scans the data
stream looking far the transmitted character
sequence LOKB. When the exact sequence is found,
the logic analyzer
fills
its memory with the next
1021 states .
Figure 3 - Glitches, which can cause the bus to
lock-up, are detected with the HP 1631A/D's
timing analyzer, and are digitized up to 200
megasamples/second with its analog capability .
The mixed display mode allows simultaneous
viewing of timing and analog.
State histograms can be used to
ensure that bus transfers are optimized
(figure 4) . Here, we can see that 25% of
the time involved the transfer of data,
indicating inefficient use of the bus .
Timing analysis and histograms can also
be performed on RS-232C/V .24 and
R S449 .
Figure 2 - The sequence LOKB was found.
Transmitted and received data, and control
functions are displayed along with their respective
input pin numbers. The HP 1630G also shows the
actual elapsed time between states . Note the bus
turn-around time when changing from transmit to
receive.
Figure 4 - Bus performance can be evaluated with
histogramming. The display shows that only 25%
of the bus activity involved data transfer .
Rewriting code could improve bus efficiency .
-ee03 .
IN 123
L 4G RTi CTS
DSR
0.00 .
- 0902 " TX E23
0 4F RTS CTS DSR
8 .334
-0001" TX 121
K 4B RTS CIS DSR 0 .332 as
+0900 " T% C21 6 42
RTS C75 DSR B .33a .5 .
" 0991 "
IT
121 9:
IT S CTS OSR 8,,339 ms
+0002 " T%, f21 HS ITS l T5 DSR
4 .332 me
" 01303 " TX 121
FF CTS OSR .Ca
8 .340 ms
,u*.u '/--x
TX 121
FF T CTS DSR CO
'0 .33] ms
.seas
2 .aoa6 Ix
131 FF
CIS
DTR DSR CV 0 .167 ."
131 FF
IS DTR 05R CD . . 35 .97 ms
"0007 BX 131
FF CTS DTR DSR CD
, 9 .115 m
"0000 RX 131 :.
FF CT5 DTR DSR CD
9 .167 m
"0009 RX 131 96
CIS .OTR DSR CD 91159 my
+0010 RX 131
96 ITS OTR OSR CO
4 .166 ms
"0011 RX 131
96 CT5 3TR DSR CO
9 .116' ms
"0012
RX 131 96
CISITR DSR CO 9 .166
ms .