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author fulivi <fulivi@users.noreply.github.com>2017-01-05 12:07:25 +0100
committer fulivi <fulivi@users.noreply.github.com>2017-01-05 12:12:33 +0100
commitd83f35b3827b5a0f486111cdbfb6171e7031e3dc (patch)
tree7ebb0b22140336fec4c0180642358ab7930aa4cd /src/devices/machine/phi.cpp
parent5a82972fe58fee742fde68766da260d46f1a7218 (diff)
hp9845: cosmetic fixes to 9895-related source files
Diffstat (limited to 'src/devices/machine/phi.cpp')
-rw-r--r--src/devices/machine/phi.cpp16
1 files changed, 12 insertions, 4 deletions
diff --git a/src/devices/machine/phi.cpp b/src/devices/machine/phi.cpp
index 2ac82a44326..34fa8d6117c 100644
--- a/src/devices/machine/phi.cpp
+++ b/src/devices/machine/phi.cpp
@@ -19,6 +19,12 @@
* C1,C2,C3,C4,C5
* HP non-standard IDENTIFY sequence
+ Fun fact: PHI has no clock input, its FSMs are driven only by
+ changes in input signals and by a few internal monostables
+
+ Main reference for this ASIC:
+ HP 12009-90001, sep 82, HP12009A HP-IB Interface Reference Manual
+
*********************************************************************/
#include "emu.h"
@@ -514,10 +520,12 @@ uint8_t phi_device::get_dio(void)
void phi_device::set_dio(uint8_t data)
{
- LOG(("DIO=%02x\n" , data));
- m_dio = data;
- if (!m_loopback) {
- m_dio_write_func(~data);
+ if (data != m_dio) {
+ LOG(("DIO=%02x\n" , data));
+ m_dio = data;
+ if (!m_loopback) {
+ m_dio_write_func(~data);
+ }
}
}