Allen-Bradley 1404-M4, Руководство пользователя

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Publication 1404-UM001D-EN-E - October 2004
8-4 Advanced Features
•
Manual increment: each write of Table A.39 specifies the
channel and block to be read in the next read of Table A.40.
Successive reads of the results table will return the same block
of data each time if no read-back select write is done.
Reading Oscillograph Data
Read oscillograph data from Table A.40 Oscillograph Results using the
indexed read method. Oscillograph data is not available via Modbus
communications. This read-only table comprises 29 (DeviceNet) or 59
(all other communications options) integer elements:
•
Capture timestamp: in three elements using the standard
timestamp format except the year is omitted
•
Capture number: in the range 1 to 8 (M6) or 1 to 2 (M8)
•
Channel number: in the range 1 to 7 (see above)
•
Block number: block number of the data contained in the table
(see above)
•
Capture type: in the range of 1 to 5 (see table above)
•
Trigger statistics: see below. Range 0 to 22,999.
•
Trigger position: data point corresponding with the trigger
position. See below.
•
Oscillograph data points: See below.
The data client sets up the read-back configuration with a table write
to Table A.39, the content of which is described above. As with other
indexed reads, DeviceNet and Ethernet optional communications
support only
manual increment read-back mode so that the client
must write a read-back select message before each read of the results
table. For all other communications options,
auto-increment all
channels or auto-increment current channel read-back mode will
provide the highest communications throughput.
Waveform Data Points
The results table contains 20 data points for optional DeviceNet
communications or 50 data points for all other communications
options. Data points are numbered 1 to 20 or 1 to 50 in each read. The
client calculates each data point’s place in the waveform using the
following formula: