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x2201: More notes (nw)

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AJR 2018-10-20 00:14:22 -04:00
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commit 994b3b39f7
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src/devices/machine/x2201.cpp
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@ -8,13 +8,18 @@
an E²PROM overlay. Besides having separate data input and output an E²PROM overlay. Besides having separate data input and output
lines (and only one of each), its interface differs slightly from lines (and only one of each), its interface differs slightly from
the later NOVRAMs in requiring an active chip select during recall the later NOVRAMs in requiring an active chip select during recall
and store operations. and store operations. The CS and STORE lines, however, may be
deactivated before the operation completes (in 2 to 4 ms).
While US patent 4535411A suggests that this device was sometimes While US patent 4535411A suggests that this device was sometimes
used in groups of eight to simulate a byte-wide memory, the used in groups of eight to simulate a byte-wide memory, the
emulation (for the most part) assumes each bit will be accessed emulation (for the most part) assumes each bit will be accessed
separately and packs them into bytes for storage efficiency. separately and packs them into bytes for storage efficiency.
X2202 has the same internal organization and data addressing as
X2201, but its recall operation works on individual bits instead
of the entire array.
**********************************************************************/ **********************************************************************/
#include "emu.h" #include "emu.h"