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-rw-r--r--src/devices/machine/mc68681.cpp4
1 files changed, 4 insertions, 0 deletions
diff --git a/src/devices/machine/mc68681.cpp b/src/devices/machine/mc68681.cpp
index 5b5d67aca92..f288a76971c 100644
--- a/src/devices/machine/mc68681.cpp
+++ b/src/devices/machine/mc68681.cpp
@@ -17,6 +17,10 @@
generates a 68000-compatible DTACK signal, instead of using generic RD and WR
strobes as the 2681 does. The 68681 also adds a programmable interrupt vector,
with an IACK input replacing IP6.
+
+ The command register addresses should never be read from. Doing so may place
+ the baud rate generator into a test mode which drives the parallel outputs with
+ internal counters and causes serial ports to operate at uncontrollable rates.
*/
#include "emu.h"