Xtal Changeon LPC932

[Joseph Goldburg]

Hi All,

The ISP baud rate is a fuction of the Xtal... this is fact.

Thus changing to a Xtal which is buad rate "unfriendly" may cause download problems?  Yes.

a.  Can somw one please advise the handshaking sequence for ISP when
 
      i)  Break Detect is programed

     ii) 3 pulse reset
 
     iii)  Jump to 1E00 hex


Does the ISP Autobaud rate detect.... what is the sequence?


Thanks in advance


Joseph

[Andy Ayre]

The usual relationship of clock speed to baudrate does not apply when using an autobaud method. That is because the device is measuring the baudrate, instead of someone calculating the exact reload value to use.

The autobaud system waits for a 'U' to be received. It then uses a short, fast loop to measure the bit times in the 'U' and calculate the approximate baudrate. As long as that baudrate is within 3% of the actual baudrate, then it will work and the device is ready to receive commands.

There are no specific crystal frequencies which cause download problems to my knowledge - only slower, but successful downloads.

Everything is described in the datasheets for the devices.