LaserSpeed 8000/9000 I/O Module Instruction Handbook
Installation
Part No. 93342 / Drawing No. 0921-01516
Page 20 of 84
Revision E (Dec 2013)
Parallel Outputs
Data is updated to the bus in one of two modes. The first is called "Data Ready"
mode and the other is called "Data Request" mode. In "Data Ready" mode, the
system will automatically update the data on the Parallel Output Bus each User
Update Period. In "Data Request" mode, the system will update the data on the
Parallel Output Bus only when a Data Requested Signal is received on the Data
Request Input Pin. There are Data Request Input Pins on the Parallel Length/
Elongation port and the Parallel Velocity port. The data output mode is
configured by
~I:AckMode
serial command:
Command
Parallel Port Mode
~I:AckMode=0
Data Ready Mode
~I:AckMode=1
Data Request Mode
Data Ready Mode
In Data Ready mode, the I/O module outputs data each time a new measurement
is received from the LaserSpeed gauge. An optically isolated signal called "Data
Ready," located on the Length/Elongation and the Velocity Output connectors,
are provided to indicate when data has been upated and is valid. The Data
Ready pulse indicates that the data bus has been updated with new data and that
the signals on the bus are completely settled. Both Data Ready True (Rising
Edge Trigger, signal driven from ground to Voltage high) and Data Ready False
(Falling Edge Trigger, signal driven from Voltage high to ground) are provided.
When using Data Ready True, data should be read from the bus on the rising
edge of the signal, and when using Data Ready False, data should be read on
the falling edge. Either the leading edge or the active level of the signal can be
used to trigger a read by your interface.
Ringing on the line can occur if the cable is not properly terminated. This can
cause the data to be unstable during the time of the active edge of the data ready
signal. Allow for extra settling time if ringing occurs.
Signal
Activity
Data Valid On:
Data Ready (True)
Active High
Rising Edge
Data Ready (False)
Active Low
Falling Edge
Data is valid from the time that the Data Ready signal is asserted until the time
that the next data point is received from the gauge. This time varies depending
on the gauge’s Update Rate configuration setting. See the timing specifications
below for detailed timing information.