Good Morning,

I have a design that implement a JESD interface between an FPGA xilinx (using its IP: JESD204B configured in TX mode) to the DAC AD9164.

The AD9164 is configured with LMF = 811 (where I have16 bit sample; 14 bit data resolution). When I generate the transport layer data packet, I understood that with F = 1, the MSB bit (D7) of any octet must change: this means that when I configure the transport layer, the control bits of the sample cannot be both on bits 15 and 14 but I have to put a control bit on D7 (octet *n*) and the second one to bit D7 (*octet n+1*) as F=1, and the Bit 7 of any octet must toggle.

This means that the D7 of any byte must be a toggled control bit.

The DAC AD9164 require to receive data with the following configuration (data sheet Rev C):

Lane 0 : M0S0[15:8]

Lane 1 : M0S0[7:0]

Lane 2 : M0S1[15:8]

Lane 3 : M0S1[7:0]

Lane 4 : M0S2[15:8]

Lane 5 : M0S2[7:0]

Lane 6 : M0S3[15:8]

Lane 7 : M0S3[7:0]

(where M is the single converter; S the four samples in a frame)

This DAC configuration require the 14 bits of data to be received on two lines (i.e.: Line 0: D13 – D8; Line 1: D7 – D0 with D15, D14 available for 2 controls bit).

My question is: how the DAC 9164 is expecting to receive the input data bytes?

In my case: D13 – D0 must be continuous data bits, and control bits on D14, D15 ?

With LMF = 811 I do not understand how I can implement a transport layer that support this configuration without toggle bit#7 any octet.

Could you help me ?

Many thanks in advance

mauriziob

Hello,

The AD9164 (all ADI DACs released to date, actually) do not support "control bits" since there is typically no need for the FPGA to convey any information about the sample to the DAC. Instead, for N=14 (14 bits converter resolution), the N'=16 (JESD204B "sample" size) is achieved by appending 2 tail bits to the LSB's of the 14-bit converter sample. So, D[15:8] = S[13:6] and D[7:0] = S[5:0],T[1:0], where S is the sample T is the tail.

An 8 lane example is covered in the Transport layer webinar on our JESD204B page and you can also find it illustrated in figure 54 of the AD9144 data sheet. In both cases the converter resolution is 16 instead of 14. The only difference is that the tail bits would be inserted into the 2 lsb's of each sample (every octet on the odd numbered lanes).

Del