3.2.13
Information Bar – Firmware Version
3.2.14
Information Bar – Thermal Error Flag
3.2.15
Information Bar – Pre-Thermal Warning
3.3
Hardware Features
3.3.1
EVM Binary Identification Code
3.3.2
RS-232 Communication Frequency
3.3.3
Impedance Matching Termination Network
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Operation
This shows the user the DSP’s firmware version.
The right side of the information bar displays three LED colors representing the thermal error flag for each
TLC5944 on the EVM. In normal operation, the error flag is a solid color. When an IC detects an
overtemperature condition, the colored circle turns into a burning IC. The EVM firmware latches the
TLC5944 overtemperature signals to ensure that the GUI is able to read and display the error signals. The
GUI can show an error condition for 2 seconds longer than the condition actually exists on the hardware.
The right side of the information bar displays three LED colors representing the pre thermal warning flag,
PTW, for each TLC5944 on the EVM. In normal operation, the error flag is a solid color. When an IC
detects a junction temperature above 120 deg, the colored circle turns into a burning IC. The EVM
firmware latches the TLC5944 PTW signals to ensure that the GUI is able to read and display the error
signals. The GUI can show an error condition for 2 seconds longer than the condition actually exists on
the hardware. Note that the PTW does not affect device operation.
Resistors R16-R27 set a binary code that is read by the DSP at start-up. The DSP communicates this
code to the GUI so that it knows what version of the EVM is connected and can load the proper software
version.
Resistors R28-R30 set a binary code that sets the default RS-232 communication frequency.
shows the available settings. The default frequency is 115.2 kbps. The user can change this setting for
custom software and communication protocol development.
Table 1. Available Settings
Default Frequency
GPIO 10
GPIO 9
9.6 kbps
0
0
57.6 kbps
0
1
115.2 kbps
1
0
Not used
1
1
Each control line contains an RC impedance matching termination network. These are shown in the lower
right corner on page 4 of the schematic. These networks are not installed and are not needed when using
the DSP board to drive the LED drivers. If the user drives the LED drivers from an external source, these
components may need to be installed to provide proper impedance matching of the PCB traces and the
external drive circuitry. Excessive ringing caused by impedance mismatch can be interpreted as
low-to-high logic level changes, causing erratic EVM behavior.
SLVU306 – April 2009
TLC5944EVM-358
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