How do I change a chip from 6-clock mode back to 12-clock mode?

[MX21]

I've got some boards that have P89LV51RD2 chips that somehow got the 6-clock (double clock) bit set.  How do I clear that?  Tried resetting, erasing all flash, etc.  There's an ISP command to set 6-clock mode, but no command to clear it.

[Andy Ayre]

You will have to check the user manual for the device from NXP. I don't have it to hand but for some devices it requires a parallel programmer and for others it is a one-way fuse and cannot be reversed.

Andy

[MX21]

You will have to check the user manual for the device from NXP. I don't have it to hand but for some devices it requires a parallel programmer and for others it is a one-way fuse and cannot be reversed.

Andy

I checked the datasheet, but I haven't been able to find any mention that you can't clear the double clock mode bit using ISP. 

[Andy Ayre]

If it doesn't explicitly say that you CAN clear it using ISP then you can't. Flash Magic only supports the commands listed in the NXP user manual. Sorry.

Andy