add link to DecoupledIO class

diff --git a/3d_gpu.mdwn b/3d_gpu.mdwn
index 6e10c6af1a28abf4c58ea396cef2ca325f87a264..7b5c458e472e6b9a0c0312ccfd6612e639434123 100644 (file)
--- a/3d_gpu.mdwn
+++ b/3d_gpu.mdwn
@@ -50,3 +50,4 @@ Progress:
 * <https://github.com/timvideos/litex-buildenv/wiki/LiteX-for-Hardware-Engineers>
 * <https://jeffrey.co.in/blog/2014/01/d-flip-flop-using-migen/>
 * <http://lists.libre-riscv.org/pipermail/libre-riscv-dev/2019-March/000705.html>
+* <https://chisel.eecs.berkeley.edu/api/latest/chisel3/util/DecoupledIO.html>