diff options
Diffstat (limited to 'control_lib/ss_rcvr.v')
-rw-r--r-- | control_lib/ss_rcvr.v | 81 |
1 files changed, 0 insertions, 81 deletions
diff --git a/control_lib/ss_rcvr.v b/control_lib/ss_rcvr.v deleted file mode 100644 index 8e650d21b..000000000 --- a/control_lib/ss_rcvr.v +++ /dev/null @@ -1,81 +0,0 @@ - - -// Source-synchronous receiver -// Assumes both clocks are at the same rate -// Relative clock phase is -// unknown -// variable -// bounded -// The output will come several cycles later than the input - -// This should synthesize efficiently in Xilinx distributed ram cells, -// which is why we use a buffer depth of 16 - -// FIXME Async reset on rxclk side? - -module ss_rcvr - #(parameter WIDTH=16) - (input rxclk, - input sysclk, - input rst, - - input [WIDTH-1:0] data_in, - output [WIDTH-1:0] data_out, - output reg clock_present); - - wire [3:0] rd_addr, wr_addr; - - // Distributed RAM - reg [WIDTH-1:0] buffer [0:15]; - always @(posedge rxclk) - buffer[wr_addr] <= data_in; - - assign data_out = buffer[rd_addr]; - - // Write address generation - reg [3:0] wr_counter; - always @(posedge rxclk or posedge rst) - if (rst) - wr_counter <= 0; - else - wr_counter <= wr_counter + 1; - - assign wr_addr = {wr_counter[3], ^wr_counter[3:2], ^wr_counter[2:1], ^wr_counter[1:0]}; - - // Read Address generation - wire [3:0] wr_ctr_sys, diff, abs_diff; - reg [3:0] wr_addr_sys_d1, wr_addr_sys_d2; - reg [3:0] rd_counter; - - assign rd_addr = {rd_counter[3], ^rd_counter[3:2], ^rd_counter[2:1], ^rd_counter[1:0]}; - - always @(posedge sysclk) - wr_addr_sys_d1 <= wr_addr; - - always @(posedge sysclk) - wr_addr_sys_d2 <= wr_addr_sys_d1; - - assign wr_ctr_sys = {wr_addr_sys_d2[3],^wr_addr_sys_d2[3:2],^wr_addr_sys_d2[3:1],^wr_addr_sys_d2[3:0]}; - - assign diff = wr_ctr_sys - rd_counter; - assign abs_diff = diff[3] ? (~diff+1) : diff; - - always @(posedge sysclk) - if(rst) - begin - clock_present <= 0; - rd_counter <= 0; - end - else - if(~clock_present) - if(abs_diff > 5) - clock_present <= 1; - else - ; - else - if(abs_diff<3) - clock_present <= 0; - else - rd_counter <= rd_counter + 1; - -endmodule // ss_rcvr |