dac8568 : CLR Pin & Software Reset

Peio,

There are three different paths in discussion here. Let me see if I can clarify.

Power-On Reset
Power-on reset functionality is for when the device is powering up. When the analog supply voltage reaches a certain threshold an OTP memory bank is read that contains a value that is latched to the DAC output. For grades A and C this OTP memory contains all zeroes such that the output value will be 0 V at power up. For grades B and D the OTP memory contains the midscale value to latch the output to miscale at power up.

Software Reset
The software reset functionality restores all register values to the reset values contained in the OTP memory, discussed previously, by triggering a Power-On Reset via software. This means that A and C grades will reset to zero scale and B and D grades will reset to mid-scale. 

CLEAR Pin
The clear pin does not trigger a Power-On Reset event. Clear simply clears the DAC output code to a code set by the clear code register. This is not a hardware reset pin.

If you wanted to use CLEAR like a hardware reset pin you simply need to put the desired value into the clear code register after power up. When you want to issue a hardware reset you would simple pulse the CLR pin and the desired value would be latched into the DAC output.

To address your question directly:

Peio Azkarate said:

Why do you need 2 different devices DAC8568A (Reset to ZERO) and DAC8568B (Reset to midscale)?. Both behaviors can be achieved by software. But from the point of view of power up both devices "RESET" to Zero.

Two different devices are offered because this functionality could not have been achieved by software since this behavior occurs on power up. Before the device has powered up you would have  had no method of communicating with it via software. This functionality could have been achieved on a single device with a pin that selects whether the device resets to zero scale or full scale, and we do that with some devices. However, in this case there was not pin real-estate available to include a pin for this functionality. 

Instead, more flexible functionality was provide via the CLR pin and the clear code registers as discussed previously. You can leverage this as though it was a hardware reset, it's just not going to restore every single register to it's default contents. It only will latch the clear code value to the DAC output.

I hope this clears things up.