TDT RZ2, Manual

Page: 358 / 736

7-44 System 3
MS4/MS16 Stimulus Isolator
Note: To conserve the life of the stimulus isolator's onboard and external batteries,
remember to power down unused bank of channels on the MS16_Control macro's
Power Control tab.
Simultaneous Stimulation on Multiple Channels and/or Local Reference Mode
The MS16_Control macro’s StimSignal is disabled whenever the local reference mode
is used or when a channel mask is used to set multiple stimulation channels. In
these cases the macro should still be used to configure or turn on channels for
stimulation (see “Configuring Reference and Stimulation Channels” on page 7-41),
but stimulus delivery must be handled external to the macro.
Converting the Signal to an Integer Value
When designing the stimulus signal it is convenient to work with floating point values
that represents the desired current in microAmps (See “Designing the Stimulus
Signal” on page 7-39), However, when the macro is not used the stimulus signal
must be converted to an integer value representing a voltage level in the proper
range for the stimulus isolator. The scale factor required to scale the current in the
desired range of +/-100 μ A is dependent on the type of base station processor
being used.
RZ5 When using the RZ5, use a scale factor of: 1.7394e+007
RX7 When using the RX7, use a scale factor of: 265.41
In this circuit segment, the desired floating point value in microAmps is fed to a
Float2Int, which converts the data type and applies the scale factor.
Signal Output to Stimulus Channels
Once output waveforms are converted to an integer value they are poked (written)
to memory locations on the MS4/MS16, using the Poke component. Memory
addresses vary be processor as described here. Reference tables are also provided
below “Memory Address Reference for Using the Poke Component” on page 7-45.
RZ5 When using the RZ5, output to channels 1-16 must be written
to memory addresses 32-47, respectively. To do so, offset the
channel number by 31 and enter this value in the address
parameter of the Poke component.
The circuit segment above sends out a stimulus signal to
channel one of the stimulator.
RX7 When using the RX7, output to channels 1-16 must be written
to memory addresses 20-35, respectively. To do so, offset the
channel number by 19 and enter this value in the address
parameter of the Poke component.