Stellaris® LM3S9B96 Development Kit User’s Manual
September 5, 2010
15
Reset
The RESETn signal into the LM3S9B96 microcontroller connects to the reset switch (SW2) and to
the ICDI circuit for a debugger-controlled reset.
External reset is asserted (active low) under any one of the three following conditions:
Power-on reset (filtered by an R-C network)
Reset push switch SW2 held down
By the ICDI circuit (U12 FT2232, U13D 74LVC125A) when instructed by the debugger (this
capability is optional, and may not be supported by all debuggers)
The LCD module has special Reset timing requirements requiring a dedicated control line from the
microcontroller.
Power Supplies
The development board requires a regulated 5.0 V power source. Jumpers JP34-36 select the
power source, with the default source being the ICDI USB connector. Only one +5 V source should
be selected at any time to avoid conflict between the power sources.
When using USB in Host mode, the power source should be set to either ICDI or to EXT if a +5 V
power supply (not included in the kit) is available.
The development board has two main power rails. A +3.3 V supply powers the microcontroller and
most other circuitry. +5 V is used by the OTG USB port and In-circuit Debug Interface (ICDI) USB
controller. A low drop-out (LDO) regulator (U5) converts the +5 V power rail to +3.3 V. Both rails
are routed to test loops for easy access.
USB
The LM3S9B96’s full-speed USB controller supports On-the-Go, Host, and Device configurations.
See Table 2-2 for USB-related signals. The 5-pin microAB OTG connector supports all three
interfaces in conjunction with the cables included in the kit.
The USB port has additional ESD protection diode arrays (D1, D2,D5) for up to 15 kV of ESD
protection.
U6, a fault-protected switch, controls and monitors power to the USB host port. USB0EPEN, the
control signal from the microcontroller, has a pull-down resistor to ensure host-port power remains
off during reset. The power switch will immediately cut power if the attached USB device draws
Table 2-2. USB-Related Signals
Microcontroller Pin
Board Function
Jumper Name
Pin 70 USB0DM
USB Data-
-
Pin 71 USB0DP
USB Data+
-
Pin 73 USB0RBIAS
USB bias resistor
-
Pin 66 USB0ID
OTG ID signal (input to microcontroller)
OTG ID
Pin 67 USB0VBUS
Vbus Level monitoring
+VBUS
Pin 34 USB0EPE
Host power enable (active high)
EPEN
Pin 35 USB0PFLT
Host power fault signal (active low)
PFLT
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