Operator`s manual

SECTION 9. INPUT/OUTPUT INSTRUCTIONS
9-10
trigger when measurement goes from above the
limit to below it or when the digital trigger goes
from high to low. When triggering on the rising
or falling edge, the input must make the
specified transition to trigger. For example,
when triggering on the rising edge, if the input
starts out high, it must go low and then high
again to trigger.
DATA SENT TO INPUT STORAGE
When the measurements are sent to Input
Storage, Parameter 6 is used to specify the
number of scans made on the channels being
measured (the 21X multiplies the number
entered by 1000). The measurements from
each channel are stored contiguously. For
example: Parameter 1 specifies 4 channels are
to be measured, Parameter 6 specifies 250
scans (0.250 entered), and Parameter 10
specifies 1 as the first input location in which to
store data. The measurements from the first
channel will be stored in Input locations 1-250,
those from the second channel in locations 251-
500, etc. If insufficient locations are allocated to
Input Storage (*A) to accommodate the number
of locations called for by Parameter 6 multiplied
by Parameter 1 (e.g., 250 x 4 = 1000), an error
code, E 60, will be displayed when the program
is compiled.
The number of scans determines how many
samples will be saved, and hence, when
Instruction 23 will be completed and execution
will pass on to the next instruction.
Measurements before and/or after the trigger
can be saved. Parameter 7 determines how
many scans that occurred prior to the trigger are
saved. For example, if 250 scans are specified,
and an offset of 20 is entered for Parameter 7,
then the trigger measurement will be stored in
Location 21. Locations 1-20 will contain the
measurements that preceded the trigger and 22-
250 will contain the measurements following the
trigger. If only 10 measurements are made
before the trigger, then they will be stored in
locations 11-20 while the value -99999. will be
stored in locations 1-10 for which no
measurements were made.
DATA SENT TO SERIAL PORT
When the raw A/D data is sent out the serial
port, the measurement data is not buffered and
hence, only the trigger and subsequent
measurements can be sent. The number of
measurements is determined by Parameters 1
and 6. Because the total number of
measurements are limited only by the storage of
the receiving computer, this can be a very large
number. Parameter 6 is the number of
measurements per channel to send in units of
1000 (e.g., 0.001 represents 1 measurement).
If 0 is entered for Parameter 6, the 21X will
continue to send data until the instruction is
aborted with the # key.
Raw A/D data may be sent to up to 2 SM192 or
SM716 Solid State Storage Modules (SM) at
76.9K baud (parameter 4, Destination Option
C=2). One SM should be set as Fill and Stop
memory and the other SM set as Ring memory.
Data sent will be stored in both SM's (in parallel)
until the Fill and Stop SM is full. The Fill and
Stop SM will store no more data. The Ring SM
will continuously store data, overwriting the
oldest data when full, until Burst measurements
end. When the Burst measurements end the Fill
and Stop SM will contain the oldest data
generated while the Ring SM will contain the
newest. If the amount of data generated
exceeds the capacity of both SM's only the
oldest and newest data will be saved. If the
amount of Burst data generated is less then the
total capacity of both SM's, part of the data
stored will be stored in both SM's. If the data is
retrieved from the SM's using SMCOM.COM, a
Storage Module communications program
contained in the PC208 Datalogger Support
Software, the data collection format must be "A
as stored 8 bit". This will transfer the raw A/D
data to a computer file. The raw A/D data can
be converted to ASCII using SPLIT.COM, a
general purpose data reduction program also
contained in PC208.
If SPLIT is not available for converting the raw
A/D, the following A/D format information is
provided for decoding purposes. At the start
and end of the series of measurements, the 21X
makes a self-calibration measurement. The
calibration data is sent at the start and end of
the measurement data. The serial data is sent
as a series of signed 2 byte integers (most
significant byte sent first; i.e., Integer = 256 *
byte 1 + byte 2): I
1
...I
n
. The first integer, I
1
, is a
start of output identifier, FCxx (hex), where the
first byte is always FC (never seen in the data),
and the second byte is a number less than 100
(decimal, 64 hex), which is the instruction