Hi TI Team,
We are trying to output PRBS under free-running VCO mode on Channel 0 with the following settings:
wrm(0xff, 0x04, 0x0f) # change to Channel 0 page
wrm(0x09, 0xfc, 0xff) # override a few controls
wrm(0x14, 0x80, 0xc0) # force signal detect
wrm(0x1b, 0x00, 0x03) # disable charge pump
wrm(0x18, 0x30, 0x70) # set VCO divider (Table 7), 4: 1/16, 3: 1/8
wrm(0x08, 0x08, 0x1f) # VCO cap count
wrm(0x1f, 0x12, 0x1f) # VCO LPF DAC
wrm(0x1e, 0x80, 0xe0) # select PRBS generator as o/p (Table 6) 4: prbs, 2: I-clock
wrm(0x1e, 0x10, 0x10) # enable PRBS
wrm(0x30, 0x08, 0x08) # toggle prbs_en_dig_clk to enable prbs output
wrm(0x30, 0x00, 0x08)
wrm(0x30, 0x08, 0x08)
wrm(0x08, 0x0e, 0x1f) # VCO cap count
wrm(0x1f, 0x14, 0x1f) # VCO LPF DAC
where wrm(register_address, value, mask) is our I2C write function
After recycling power of the EVM board and running the above code, we manage to see data output at a rate of 1.25Gbps. However, what's strange is that we get a very short repetitive pattern like below:
1111 0100 1010 0000
Can you explain why that happens and how we can fix it (ie. to get the default PRBS-7 pattern)?
Thanks.
