diff --git a/doc/CHANGELOG.md b/doc/CHANGELOG.md
index ac4d5818..fce5c83f 100644
--- a/doc/CHANGELOG.md
+++ b/doc/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ### Table of contents
 - Current [HEAD](#user-content-head)
+- Release [w11a_V0.77](#user-content-w11a_V0.77)
 - Release [w11a_V0.76](#user-content-w11a_V0.76)
 - Release [w11a_V0.753](#user-content-w11a_V0.753)
 - Release [w11a_V0.752](#user-content-w11a_V0.752)
@@ -22,6 +23,20 @@ software or firmware builds or that the documentation is consistent.
 The full set of tests is only run for tagged releases.
 
 ### Summary
+### New features
+### Changes
+### Bug Fixes
+### Known issues
+
+<!-- --------------------------------------------------------------------- -->
+---
+## <a id="w11a_V0.77">2019-04-28: [w11a_V0.77](https://github.com/wfjm/w11/releases/tag/w11a_V0.77) - rev 1141(wfjm)</a>
+### Summary
+- add support for buffered character interfaces
+  - LP11: ibdr_lp11_buf
+  - PC11: ibdr_pc11_buf
+  - DL11: ibdr_dl11_buf
+- add mcodes: new test and demonstration codes
 
 ### New features
 - new components
diff --git a/rtl/w11a/tb/tb_rlink_tba_pdp11core_ibdr.dat b/rtl/w11a/tb/tb_rlink_tba_pdp11core_ibdr.dat
index 634e22b7..3a2f560a 100644
--- a/rtl/w11a/tb/tb_rlink_tba_pdp11core_ibdr.dat
+++ b/rtl/w11a/tb/tb_rlink_tba_pdp11core_ibdr.dat
@@ -2,7 +2,7 @@
 #
 #  Revision History: 
 # Date         Rev Version  Comment
-# 2019-04-06  1126   1.6    adapt to new dl11 iface
+# 2019-04-28  1141   1.6    adapt to new dl11 iface
 # 2015-05-03   674   1.5    start/stop/suspend overhaul
 # 2014-12-26   621   1.4    adapt wmembe,ribr,wibr testing to new 4k window
 # 2014-09-27   595   1.3    now for rlink v4 iface
@@ -143,10 +143,11 @@ C -----------------------------------------------------------------------------
 C test device attention (use DL11 XCSR/XBUF [177564/177566])
 #
 rreg .XCSR      d=o"000200"             -- read  XCSR via RRI: XRDY=1
-rreg .RBUF      d=o"100000"             -- read  RBUF via RRI: RRDY=1
+rreg .RBUF      d=o"000000"             -- read  RBUF via RRI: RSIZE=0
 rreg .XBUF      d=o"000000"             -- read  XBUF via RRI: XDONE=0
 wreg .al          o"177566"             -- #XBUF
 wreg .mem         o"000123" s=00001000  -- write XBUF via CPU
+rreg .RBUF      d=o"000001" s=00001000  -- read  RBUF via RRI: RSIZE=1
 rreg .XCSR      d=o"000000" s=00001000  -- read  XCSR via RRI: XRDY=0
 rreg .XBUF      d=o"100523" s=00001000  -- read  XBUF via RRI: VAL,VAL8=1
 rreg .XBUF      d=o"000123" s=00001000  -- read2 XBUF via RRI: VAL,VAL8=0