Hi, does anyone know how the oscillation mode is determined in an LPC2148? Page 18 of the manual starts talking about how there is a "slave" mode and an "oscillation mode", but I can't find anywhere that discusses how these are actually selected. Does anyone know or see it?
Secondly, what is the frequency if the internal oscillator? (Where do you find this?)
Hi, does anyone know how the oscillation mode is determined in an LPC2148? Page 18 of the manual starts talking about how there is a "slave" mode and an "oscillation mode", but I can't find anywhere that discusses how these are actually selected. Does anyone know or see it?
I could be totally wrong, but by "mode" I think they just mean what type of oscillator source you have connected. You can use either a crystal connected to both X1 and X2 pins (master), or an outboard clock source (another MCU or whatever?) connected to just the X1 pin (slave). I looked at all the docs I have here and found no reference (so far) to "selecting" the mode.
Secondly, what is the frequency if the internal oscillator? (Where do you find this?)
As far as I know there is no internal oscillator. F_OSC is the clock rate of the oscillator you have connected. You can multiply that up internally with the PLL, but the oscillator base clock is still external.
The oscillator output frequency is called FOSC and the ARM processor clock frequency is referred to as CCLK for purposes of rate equations, etc. elsewhere in this document. FOSC and CCLK are the same value unless the PLL is running and connected.
Ah, that makes lots of sense. I'm not sure what gave me the idea that there was an internal clock, but I've been agonizing over this for a while . Thanks!
This means it works in 2 modes obviously lol but there is infact no actual register to select it. The actual way to do it is in HARDWARE. They way you have it connected determines if its in SLAVE or OSC. Mode.
Check out page 19 the diagram:
I think this is in-fact how you set the mode of operation.