PULL UP missing on the OSBDM ?

[naej_gz]

Hy

After a reset, the state of PTC1 is unknown. if PTC1 is low, the direction of 1T45 is B to A.

Therefore, the pull up resistor on PTA1 has no effect an the state of PTA1 is unknown.

The chip may be difficult to program using the mon08 connector because of this unknown state of PTA1. 

any body has an idea about this ? 

bye Jean

[pgo]

Dear naej_gz,

Most of the OSBDMs would be programmed using the USB ICP feature that does not require A.1 to be any particular level.  As you indicated, the floating pins might interfere with the MON08 interface but this would only be needed if being de-bugged.

bye

Message Edited by pgo on 2009-04-08 02:24 PM

[peg]

Hi,

In addition most well designed MON08 adapters would include a pullup within the adapter.

[pgo]

Dear Peg,

The missing pull-up is on C.1 which isn't on the MON08 interface so naej_gz still has a point I think.

bye

[peg]

Hi,

Yeah, knew I should have looked at the circuit first. (C1 is in a lot of other MON08 interfaces)

Also A1 is a don't care when blank so you can get the initial code in the first time at either level.

I guess things must tend to favour the OK levels here to get it to work.

I know I have re-programmed and debugged many times ( a long time ago) without any issues over the MON08 interface as well as USB.

[naej_gz]

Hy

If you accept same probability for every floating input state  (i'm not sure of that)

the chance is 1/2 for wrong direction of translator chip (otherwise the pull up on PTA1 works fine), then 1/2 for wrong state of translator input.

therefore the chance is only 1/4 to get a trouble (not entering monitor state)

may that explain the problem was not seen ?

bye 

and thanks for your answers