On Mon, Apr 18, 2011 at 23:18, Eric Decker <[email protected]> wrote: > That is a good. thing. On the mm4 mote (2618 based) I have a SD card that > is > driven off of an SPI and I want it to run as fast as possible so I did > something > similar. All the peripherals are run off SMCLK. In general the SMCLK > should > be run as fast as possible. It is unclear why the original choice of SMCLK > = DCO/4 > was chosen. Maybe Vlado can comment, I'm pretty sure he was there. >
I guess there are several reasons for the SMCLK=1MHz decision. First this config has long tradition in the general msp430 community and TI example code) and was considered a safe choice for the set of peripheral chips that we had to support at that time. For example, 500 kHz SPI bus clock is pushing the limits of the TDA5250 radio on eyesIFX. >> >> The SFD pin of the CC2420 is connected to pin on the MSP430 that can >> capture timer/counter B but not timer/counter A. Therefore, to be able >> to timestamp with the microsecond clock, timer B must be clocked at >> 1uis, and timer A should be programmed as the 32kHz clock. (Currently, >> timer A is running at 1uis, and timer B at 32kHz.) > >> >> One potential difference from the original clock setup is that in this >> case we are left with only 3 timer compare interfaces for the >> 32khz/1mis clocks, versus 7 in the original case. > > Actually, putting the 1mis clock on TimerA gives 3 CCRs and the 1uis clock > on TimerB gives 7 CCRs for the uis clock. > >> But since the 1mis >> clock is virtualized, this should not be a limitation. > > In practice the additonal compare capture registers aren't utilized. If > they do get > used it is a special app that needs to handle the situation itself. There are many platform-specific telosB applications out there that use more than three jiffy alarms, so I would be very careful with going down this road only because of the way the CC2420 SFD is wired or not wired to the MCU on a given platform. Vlado
_______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
