05-14-2014 11:51 AM
I'm trying to use the XM104 board on with the VC707 board.
Additionally, I need to be able to program the Si570 on the XM104 to generate a 125 or 625MHz clock.
I've set the PCA9548 switch on the VC707 to connect to the I2C bus on the FMC1,
and I understand I need to program the PCA9543 switch on the XM104 to interact with the Si570 chip.
The datasheet for the PCA9548 gives me an 8-bit address which includes a r/w bit, which I understand can be used as a 7 bit address without the r/w bit.
However, it includes two bits which is not fixed, and can be set from the FPGA board, connected to GA0 and GA1.
I could not find anything online how the GA0 and GA1 values are set. They seem to exist as pins on the FMC diagram, but not on the master ucf/xdc file.
Furthermore, I tried reading from all 4 possible addresses, 0x70 to 0x73, which all returned 0xFF.
Setting all of them to 0x01 does not let me access the Si570 either.
Is there something obvious I am missing?
Thanks to everyone in advance!
05-14-2014 12:45 PM
The VC707 User Guide as a list of the I2C addresses including for the FMC1 and FMC2 in Table 1-24.
05-14-2014 02:18 PM
First of all, thank you for the quick reply :)
I am aware of the table.
However, this one is about programming the PCA9458 on the VC707 board itself,
which is on the 0x74 address. I have programmed it to connect to the XM104 board on FMC 1 by sending the value '1' to address 0x74.
My problem is that there is another switch on the XM104 board, the PCA9543 1-to-2 switch, and I can't seem to address that one...
05-14-2014 03:43 PM
Ah it seems writing to all 4 different combinations of the i2c address was working after all (0x70 to 0x73)
It was just that the registers were being reset after enabling the clock and setting unfreeze.
I suppose it's an issue with the Si570 clock. I'll try to figure it out.
05-14-2014 04:50 PM
Table 1-24 in the VC707 User Guide UG885 has the I2C address of the downstream devices that are connected to the VC707 base board PCA9548 and this includes the FMC1 and FMC2 connectors. The address shown for both of these is 0bXXXXX00 indicating that the GA0 and GA1 are connected to ground or logic 0. The VC707 schematics will also show these pins grounded. I do understand that this is not crystal clear from the table and have passed along the feedback to the author that a foot note should be added to the table as well as an explict mention in the FMC1 and FMC2 sections on pages 58-59.
When you write through to the XM104 the address is then 0x70 as the fixed portion is 111_00xx and the lower two bits (xx) are connected to GA0:1 as shown on the schematic and the XM105 User Guide, UG536.