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clock problems

bleumers_j
Associate II
Posted on July 09, 2003 at 14:06

clock problems

6 REPLIES 6
bleumers_j
Associate II
Posted on June 27, 2003 at 09:30

Hello,

When i mount an 8MHz crystal on my board with 2x 47pF to ground and i switch off the RC-oscillator, the ST7 seems to 'die'.

I can't read or write anymore with the ST-Stick and the program doesn't run.

When i put the scope on the crystal, the clock doesn't run.

Anyone an idea what's going wrong???

Regards.
stephanie
Associate II
Posted on July 02, 2003 at 07:46

What is your device? Did you configure the right oscillator range in option bytes? Which ICP did you choose in STVP7 (OPT disable or enable)?

drumfirex
Associate II
Posted on July 02, 2003 at 09:23

I never used RC-oscillator (not internal nor external) so I'm not sure abuot the following procedure...

I'm programming on ST72324 using inDart.

If you use a crystal you should set ''Resonator Oscillator'' in the option bytes.

You should program the option bytes when the uC is ''alive'', so:

- switch on RC-oscillator

- reprogram option bytes with ''Resonator Oscillator''

- connect the crystal and switch off the RC-oscillator

In the 72324 datasheet, typical values of capacitors (for a 8MHz xtal) are 33pF each.

I hope that can help,

Patrik
bleumers_j
Associate II
Posted on July 02, 2003 at 13:38

Hi,

Programming is OPT enable. Had the problem with the st7lite29 and with the st7dali. I'm using an 8MHz crystall.

I choose the 4/8MHz Medium Speed resonator, program this. After doing this (like Patrik told) i switch off the internal oscillator and program the option bytes for a second time. After this the IC died...

I must do something wrong but i can't figure out what.

Greets

drumfirex
Associate II
Posted on July 03, 2003 at 09:32

The signal on the crystal is present only if the option bytes are set correctly. I set two option bytes as follow:

- [OSCRANGE] - Oscillator Range Selection: ''MS: 4-8MHz''

- [OSCTYPE] - Oscillator Type Slection: ''Resonator Oscillator''

Bye,

Patrik
stephanie
Associate II
Posted on July 09, 2003 at 14:06

The right way to proceed is the following one:

* as by default, the clock is internal RC, program your Flash

* then the option byte (no matter if the quartz is already on the appli board, it will be ignored when configured in internal RC thanks to internal switches): Resonnator oscillator, oscillator mid-range, internal RC off + the other options

* remove your ICC cable

* make a reset of the MCU