Getting a DS89C450 working off program board

[Derill03]

what is the correct logic state for the /EA, RST, /PSEN, and ALE/PROG on a DS89C450

 

[ctownsend]

in program mode or run mode?

I would think you could get all that information from the datasheet.

 

[Derill03]

In run mode

Added after 25 minutes:

currently i have /EA pulled high, and /PSEN and ALE/PROG are floating. The RST is pulled low. When i power the chip up it needs a high-to-low transition to run code. I was told by dallas semi that it does not need a transition. Any help, I don't care about program mode at this point.

 

[Derill03]

The high-low transition is needed on the RST pin

 

[ctownsend]

The high-low transition is needed on the RST pin

I think you got that backwards.
low-high transition is what it takes.

Its difficult to see your problem without knowledge of your board or a schematic to look at.

 

[subyraj]

make the PSEN pulled high

 

[wek]

This might be a case of problematic power startup, as stated in datasheet at a comment for the V(RST) - reset trip point - note 3 at page 3:

The user should note that this part is tested and guaranteed to operate down to 4.5V (10%) and that VRST (min) is specified below that point. This indicates that there is a range of voltages [VMIN to V RST(min)] where the processor's operation is not guaranteed, but the reset trip point has not been reached. This should not be an issue in most applications, but should be considered when proper operation must be maintained at all times. For these applications, it may be desirable to use a more accurate external reset.

Also, I think you shouldn't tie /RESET to GND hard, as it is a bidirectional pin (it attempts to output high when the internal reset is active). You might want to leave /RESET pin floating (or pulled low weakly) and look at that output level; as well as look at whether and how the oscillator starts at powerup, together with looking at the VCC/GND directly at the mcu's power pins, for irregularities during powerup.

I would be glad to hear here about your findings.

JW