> How would I go about setting the four GPIO points on an FT232 chip to > be used as a JTAG device? These points are: > CBUS0 ...
There are a few caveats with these. First, the CBUS bitbang mode has to be set up in the EEPROM. It is not possible to setup CBUS bitbang mode if it is not configured already in the EEPROM. > Basically I am asking if anyone has had a reason to accomplish this? Second, is it - as far as I know - only possible to change and or read the pin state using the commands FT_SetBitMode and FT_GetBitMode. They take at least 1ms to complete. Therefore you can't go beyond 500 Hz bit rate (toggling TCK takes two commands) when sending or even less when sending and receiving data. Therefore, you don't want to use this chip primarily for JTAG on CBUS pins. It /might/ be used as a very, very last resort to reconfigure JTAG targets such as CPLDs or small microcontrollers in the field. But... : > Obviously when the part is being used this way the UART end is not > usable. Third, the pins loose their CBUS state and direction while the FT232 is in normal (serial) operating mode. As far as I remember from earlier experiments, even if you find a configuration in which they "should" retain the same state while switching from bit bang to serial mode, there are some clock cycles while switching in which they become tristated. You would have to spend some time to find a setup in which the JTAG pins are guaranteed not to disturb the normal operation regardless what's happening there.. Kolja > ----- > Gregg C Levine [email protected] > "This signature fought the Time Wars, time and again." > > ------------------------------------------------------------------------------ > This SF.net email is sponsored by Sprint > What will you do first with EVO, the first 4G phone? > Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first > _______________________________________________ > UrJTAG-development mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/urjtag-development > ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first _______________________________________________ UrJTAG-development mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/urjtag-development
