Hi all
I have some questions about mcf52211's clock module,hope you can geive me some explanations
1. the CLKMOD[1:0] Pins determine clock mode during POR, The 52211 reference manual says:
CLKMOD[1:0] XTAL Clocking Mode
00 0 PLL disabled, clock driven by external oscillator
00 1 PLL disabled, clock driven by on-chip oscillator
01 N/A PLL disabled, clock driven by external crystal
10 0 PLL in normal mode, clock driven by external oscillator
10 1 PLL in normal mode, clock driven by on-chip oscillator
11 N/A PLL in normal mode, clock driven by external crystal
my question is if I use MCF52211CAE66 (LQFP64 package), which has not CLKMOD1 pin, how about the clock mode during POR? for example if I connect CLKMOD0 pin to VCC33, what is the clock mode ?
2.The CCLR register select clock source, reference manual's table 6-11 says:
Table 6-11. CCLR[OSCSEL1] and CCLR[OSCSEL0] Settings
OSCSEL1 OSCSEL0 Source of PLL input/bypass clock
0 0 Primary oscillator (default)
0 1 Relaxation oscillator
1 0
Secondary oscillator
1 1
my question is what is Primary oscillator and what is secondary oscillator?
thanks!
Solved! Go to Solution.
Hi
The CLKMOD pins have internal pull downs. This means that CLKMOD[1] will default to '0' when the pin is not available on the smaller package. The PLL will thus always be disabled by default.
Generally the default setting is not critical since the start-up code can immediately overwrite the setting.
I believe that the secondary oscillator is referring to the external oscillator but I don't remember using this mode, so can't be sure. Unfortunately the manual description of the OSCSEL1 bit doesn't seem to correspond to the table 6-11 so a test is probably the fastest way to be sure...
Regards
Mark
www.uTasker.com
- OS, TCP/IP stack, USB, device drivers and simulator for M521X, M521XX, M5221X, M5222X, M5223X, M5225X. One package does them all - "Embedding it better..."
Hi
The CLKMOD pins have internal pull downs. This means that CLKMOD[1] will default to '0' when the pin is not available on the smaller package. The PLL will thus always be disabled by default.
Generally the default setting is not critical since the start-up code can immediately overwrite the setting.
I believe that the secondary oscillator is referring to the external oscillator but I don't remember using this mode, so can't be sure. Unfortunately the manual description of the OSCSEL1 bit doesn't seem to correspond to the table 6-11 so a test is probably the fastest way to be sure...
Regards
Mark
www.uTasker.com
- OS, TCP/IP stack, USB, device drivers and simulator for M521X, M521XX, M5221X, M5222X, M5223X, M5225X. One package does them all - "Embedding it better..."