diff --git a/tcl/interface/ftdi/digilent-hs2.cfg b/tcl/interface/ftdi/digilent-hs2.cfg
index 9501c4ad4..89c9e4b6c 100644
--- a/tcl/interface/ftdi/digilent-hs2.cfg
+++ b/tcl/interface/ftdi/digilent-hs2.cfg
@@ -2,6 +2,10 @@
 
 # this supports JTAG-HS2 (and apparently Nexys4 as well)
 
+# ADBUS5 controls TMS tri-state buffer enable
+# ACBUS6=SEL_TMS controls mux to TMS output buffer: 0=TMS 1=TDI
+# ACBUS5=SEL_TDO controls mux to TDO input: 0=TDO 1=TMS
+
 adapter driver ftdi
 ftdi device_desc "Digilent Adept USB Device"
 ftdi vid_pid 0x0403 0x6014