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-rw-r--r--src/devices/machine/adc0804.cpp7
1 files changed, 7 insertions, 0 deletions
diff --git a/src/devices/machine/adc0804.cpp b/src/devices/machine/adc0804.cpp
index ad39b1d8e81..aad5b88ffb3 100644
--- a/src/devices/machine/adc0804.cpp
+++ b/src/devices/machine/adc0804.cpp
@@ -26,6 +26,13 @@
multiple other devices are also clocked through pin 19, which
yields the output of the internal Schmitt trigger clock circuit.
+ The ADC0804's INTR semaphore output reflects not the actual busy
+ state of the converter (as EOC does on the ADC0808) but an
+ internal flip-flop attached to it. This flip-flop is reset by
+ pulling either RD or WR active low; therefore, INTR will never
+ toggle if RD is tied to GND to keep the data outputs continuously
+ active.
+
**********************************************************************/
#include "emu.h"