Honored Contributor
Honored ContributorYou need to download and install the kit documentation. The schematic should be in there somewhere. Go and have a look at it to see what those pins connect to.
The HSMC specification defines a 'recommended' pin out for the connector. The Management bus is just an I2C interface. Its likely that its just connected to GPIO pins on the FPGA. There might be a pull-up to 3.3V. The GPIOs pins might be in a 2.5V bank. For an I2C application, they would have only been driven low, and the 3.3V pull-up would have generated the high. If that is true, then you can drive these signals high or low (the high will be whatever the bank VCCIO is). If you need to receive 3.3V, then you should review the handbook regarding maximum voltages. The same comments apply to the CMOS clock out pin - if its connected to a GPIO, then you can use it as you like. The reason for the HSMC specifying those pins with a particular function or direction is that it allows daughter card manufacturers to implement their hardware to adhere to the spec. When you're developing your own daughter card for a specific FPGA board, you just need to make them compatible. Note that you might not be able to use your board with another development kit, so try to keep things compatible if you think you might want to use your daughter board with a different kit, eg., put some series resistors in the path between your daughter card signal driving the CMOS clock out pin on the HSMC, so that you can isolate your daughter card driver from the CMOS clock out driver on a different kit. Cheers, Dave
