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-rw-r--r--usrp2/timing/time_compare.v26
-rw-r--r--usrp2/vrt/vita_tx_control.v5
2 files changed, 27 insertions, 4 deletions
diff --git a/usrp2/timing/time_compare.v b/usrp2/timing/time_compare.v
index a21c9f8e0..cb2b6d860 100644
--- a/usrp2/timing/time_compare.v
+++ b/usrp2/timing/time_compare.v
@@ -14,10 +14,34 @@ module time_compare
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 = (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
diff --git a/usrp2/vrt/vita_tx_control.v b/usrp2/vrt/vita_tx_control.v
index 967847d36..ddcb6a2d2 100644
--- a/usrp2/vrt/vita_tx_control.v
+++ b/usrp2/vrt/vita_tx_control.v
@@ -38,9 +38,8 @@ module vita_tx_control
// FIXME ignore too_early for now for timing reasons
assign too_early = 0;
time_compare
- time_compare (.time_now(vita_time), .trigger_time(send_time), .now(now), .early(early),
- .late(late), .too_early());
-// .late(late), .too_early(too_early));
+ time_compare (.time_now(vita_time), .trigger_time(send_time),
+ .now(now), .early(early), .late(late), .too_early());
localparam IBS_IDLE = 0;
localparam IBS_RUN = 1; // FIXME do we need this?