The devices MSP430F565x and MSP430F665x come preprogrammed with the USB BSL. Use of the USB BSL requires external access to six pins (see Table 6-5). In addition to these pins, the application must support external components necessary for normal USB operation; for example, the proper crystal on XT2IN and XT2OUT or proper decoupling.
|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 application is invoking the BSL, 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.