All devices come preprogrammed with the USB BSL. Use of the USB BSL requires external access to six pins (see Table 6-3). In addition to these pins, the application must support external components necessary for normal USB operation (for example, proper crystal on XT2IN and XT2OUT and proper decoupling). For further details on interfacing to development tools and device programmers, see the MSP430 Hardware Tools User's Guide.
|DEVICE SIGNAL||BSL FUNCTION|
|RST/NMI/SBWTDIO||Entry sequence signal|
|PU.0/DP||USB data terminal DP|
|PU.1/DM||USB data terminal DM|
|PUR||USB pullup resistor terminal|
|VBUS||USB bus power supply|
|VSSU||USB ground supply|
The default USB BSL evaluates the logic level of the PUR pin after a BOR reset. If it is pulled high externally, then the BSL is invoked. Therefore, unless the BSL should be invoked, it is important to keep PUR pulled low after a BOR reset, even if BSL or USB is never used. TI recommends applying a 1-MΩ resistor to ground.