Due to a problem in the Intel® Quartus® Prime Software version 19.1, you may see simulation read errors when you set the data configuration to “Differential.”
To work around these problems, open the *phylite_io_bufs.sv file under the altera_phylite_arch_nf_*\sim directory.
Change the line from:
assign group_data_out_n [grp_num][47 : GROUP_PIN_WIDTH[grp_num]-1]={(MAX_WIDTH-GROUP_PIN_WIDTH[grp_num]){1'b0}};
to:
assign group_data_out_n [grp_num][47 : GROUP_PIN_WIDTH[grp_num]]={(MAX_WIDTH-GROUP_PIN_WIDTH[grp_num] 1){1'b0}};
This problem is fixed starting with the Intel® Quartus® Prime Software version 19.3.