ADSP-SC589 EZ-Board® Evaluation System Manual
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3.2.1 Overview of SoftConfig
In order to further clarify the use of electronic single FET switches and multi-channel bus switches, an
example of each is illustrated and compared to a traditional mechanical switching solution. This is a
generic example that uses the same FET and bus switch components that are on the EZ-Board.
After this generic discussion there is a detailed -explanation of the SoftConfig interface specific to the
ADSP-SC589 EZ-Board.
The circuit below shows two individual FET switches (Pericom PI3A125CEX) with reference
designators UA and UB. Net names ENABLE_A and ENABLE_B control UA and UB. The default
FET switch enable settings in this example are controlled by resistors RA and RB which pull the
enable pin 1 of UA and UB to ground (low). In a real example, these enable signals are controlled by
the Microchip IO expander. The default pull-down resistors connect the signals
EXAMPLE_SIGNAL_A and EXAMPLE_SIGNAL_B and also connect signals
EXAMPLE_SIGNAL_C and EXAMPLE_SIGNAL_D. To disconnect EXAMPLE_SIGNAL_A from
EXAMPLE_SIGNAL_B, the Microchip IO expander is used to change ENABLE_A to a logic 1
through software that interfaces with the Microchip. The same procedure for ENABLE_B would
disconnect EXAMPLE_SIGNAL_C from EXAMPLE_SIGNAL_D.
The image below shows the equivalent circuit as above but utilizes mechanical switches that are in the
same package. Notice the default is shown by black boxes located closer to the ON label of the
switches. In order to disconnect these switches, physically move the switch to the OFF position.
