diff options
Diffstat (limited to 'usrp2/timing/time_compare.v')
-rw-r--r-- | usrp2/timing/time_compare.v | 44 |
1 files changed, 7 insertions, 37 deletions
diff --git a/usrp2/timing/time_compare.v b/usrp2/timing/time_compare.v index 54ea000d6..21607f51c 100644 --- a/usrp2/timing/time_compare.v +++ b/usrp2/timing/time_compare.v @@ -1,5 +1,5 @@ // -// Copyright 2011 Ettus Research LLC +// Copyright 2011-2012 Ettus Research LLC // // This program is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by @@ -16,49 +16,19 @@ // -// Top 32 bits are integer seconds, bottom 32 are clock ticks within a second +// 64 bits worth of ticks module time_compare (input [63:0] time_now, input [63:0] trigger_time, output now, output early, - output late, + output late, output too_early); - - wire sec_match = (time_now[63:32] == trigger_time[63:32]); - wire sec_late = (time_now[63:32] > trigger_time[63:32]); - wire tick_match = (time_now[31:0] == trigger_time[31:0]); - wire tick_late = (time_now[31:0] > trigger_time[31:0]); -/* - assign now = sec_match & tick_match; - assign late = sec_late | (sec_match & tick_late); - assign early = ~now & ~late; -*/ + assign now = time_now == trigger_time; + assign late = time_now > trigger_time; + assign early = ~now & ~late; + assign too_early = 0; //not implemented - /* - assign now = (time_now == trigger_time); - assign late = (time_now > trigger_time); - assign early = (time_now < trigger_time); - */ - - // Compare fewer bits instead of 64 to speed up logic - // Unused bits are not significant - // Top bit of seconds would put us in year 2038, long after - // the warranty has run out :) - // Top 5 bits of ticks are always zero for clocks less than 134MHz - // "late" can drop bottom few bits of ticks, and just delay signaling - // of late. - // "now" cannot drop those bits, it needs to be exact. - - wire [57:0] short_now = {time_now[62:32],time_now[26:0]}; - wire [57:0] short_trig = {trigger_time[62:32],trigger_time[26:0]}; - - assign now = (short_now == short_trig); - assign late = (short_now[57:5] > short_trig[57:5]); - assign early = (short_now < short_trig); - - assign too_early = (trigger_time[63:32] > (time_now[63:32] + 4)); // Don't wait too long - endmodule // time_compare |