On Monday 31 August 2009, Jonas Horberg wrote: > I think than the board config file is the right place to put speed > settings. It will benefit the end users if we provide good clock speed > settings in the scripts that is shipped with OpenOCD.
That's probably the best place to have defaults, or (if you will) upper limits. Yes. > The maximum JTAG clock speed is mostly dependent of board specific > things. Some examples: > * The devices in the JTAG chain of the board. > * The CPU clock source/speed. > * Different source/speed before and after reset init. Some board > files have scripts that change the clock source/speed at specific > events. Necessary if adaptive clocking is not supported. An example would be the AT91 chips that come up with a 32 KHz system clock after they reset ... and need either boot code, or reset-init scripts, to set up oscillators and PLLs before fast clocks can be used, and JTAG can be used at multi-mbit data rates. > * The routing of the JTAG wires. > * Board support of RTCK. > > The interface driver should only set the speed to the requested or the > closest lower supported speed. I do not think there is any problem > running with a lower speed than the requested. All true. I suspect the thing I was thinking of when I said "openocd.cfg" is that it also depends on how the board boots ... and with JTAG you may well be debugging boot code. Or recovering a bricked board; in both cases, the board defaults likely won't help. > The type and length of the cable that connects the interface to the > board and also the interface driver strength have some influence. > I think it is minor, but it is possible that we should be a bit > conservative when we select the clock speed for the board scripts. > > If the board support RTCK (its MCU support it and it is routed to > the JTAG connector, please consider to use the jtag_rclk instead of > jtag_khz. It will fall back to a fixed clock speed if the interface > do not support RTCK. > _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
