How fast is the speed of BDC clock for MC9S08GT16CFB generally?

[jjl3]

I am trying to make a BDM for MC9S08GT16CFB.

I use the demo borad of DSP56F901A60 as BDM.

after I sent SYNC signal to target MCU(MC9S08GT16CFB),

I might receive low pulse from target MCU.

I use the counter in DSP56F801A60(also use internal clock source.IPbus =30MHz.Primary Count Source of counter is IPBus clock divide by 1) to measure,

the result is 0x3c9. so the speed of BDC = 0x3c9 / 128 = 7 IPBus clocks.

I suspect whether the speed of BDC is real fast like above???

if fast like above, it is very difficult to program for DSP56F801A60 to simulate the timing of BDC communication.  because the cycles of some instructions are usually 2,3,even 6 IPBus clocks, it will product big error :-(

[peg]

Hi,

The BDM clock for the GT/GB is either BUSCLK (whatever you have that set to) or the 8MHz ICGLCLK. This is selected by the CLKSW bit in the BDMSCR register.

Regards David

[jjl3]

Hello, David

Thanks for your reply!

as for so fast speed of BDC clock(8MHz),

could you recommend  how to product precise timing for BDC communication when using DSP56F801A60 as a BDM?

Thanks & BR

ji junli

[peg]

Hi jjl3,

You only have to be accurate to "a few percent"

I know very detail about the DSP you mention but, the job gets done by 8 bit QT and JB processors running at 4MHz so I am sure you can get it done with your processor.

Why don't you have a look at the other BDM designs, I have listed them in this thread:

http://forums.freescale.com/freescale/board/message?board.id=16BITCOMM&message.id=1597

Regards David

Message Edited by peg on 2006-07-27 10:02 PM

[jjl3]

Thanks for your warm help!