Scaler II vs Scaler problems

Hi Niki,

I'm glad you have found the problem and that the Scaler II is not broken. The reason it initially worked for the Scaler and not the Scaler II is that the old Scaler uses native addressing and the Scaler II uses dynamic addressing.

With native addressing each word written by the master writes to one word of the slave, regardless if their data widths. This leads to cropping or padding of data when the widths don't match. In your case you will only ever write to the bottom 16 bits of the Scaler's control registers, but this is OK because the resolutions you were wrting were less than 16 bits wide.

With dynamic addressing byte enables are used to supliment the conversion between the master and slave addresses so that every byte of data written at the master is written to the slave, and every btye read by the master is useful data from the slave. Hence, when a 16 bit master wirtes to a 32 bit slave, the bottom two bits of the master address are converted into byte enable signals at the slave

- address 0 at the master will write to the bottom two bytes of register 0 at the slave

- address 2 at the master will write to the top two bytes of register 0 at the slave

....and so on. This means that your writes to byte adresses 6 and 8 (to update output resolutions) will have been written to the top half of register 1 and the bottom half of register 2 in the Scaler II slave (instead of registers 3 and 4).

The change to dynamic adressing in the Scaler II has been driven by the deprication of native adressing in SOPC Builder. The downside is that, with native adressing, the user never needs to know the width of the slave registers, so long as their master is wide enough to convey the desired data. Hence there was no need to explicitly state it in the user guide (I'm guessing). With dynamic addressing you do need to know the width of the slave to work out where all your bytes of data will end up. A note should definitely be added to the user guide to make all this explicit. Perhaps this will happen.

Good luck with the rest of your design.

Regards,

Kieron