Bus: Pinout and a little description of RC6502 bus

Bus.md

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+RC6502 Bus
+==========
+
+The RC6502 system uses a 39-pin bus; the physical layout is a single
+row of 0.05" square header pins on 0.1" centers. Conventionally the
+boards have a male right-angle connector on one edge and these are
+plugged into a [backplane] with female connectors.
+
+The pinout is as follows. The signal directions (input or output from
+the point of view of CPU and peripheral boards, respectively) are
+guidelines, and a specific board might have a different direction. For
+signals where both are marked `in`, both CPU and peripheral boards are
+usually capable of using the signal as an input, but it's expected
+that one board in the system will be generating the signal.
+
+    Signal  Pin  CPU Periph
+      Name  No.  Dir. Dir.   Notes
+    --------------------------------------------------------------
+       A15   1   out   in
+         …  …
+        A0  16   out   in
+       GND  17   in    in
+       Vcc  18   in    in
+     Φ2out  19   in    in
+    /RESET  20   in    in    Must be actively controlled by one board
+      Φ0in  21   in    in
+      /IRQ  22   in    in    Pull-up req'd; usually provided by CPU board
+     Φ1out  23   in    in    Sometimes called EX0
+       R/W̅  24   out   in
+       RDY  25   in    out
+      SYNC  26   out   in
+        D0  27   ↔     ↔
+         …  …
+        D7  34   ↔     ↔
+        TX  35   ?     ?
+        RX  36   ?     ?
+      /NMI  37   in    out   Pull-up req'd; usually provided by CPU board
+         ×  38               Also known as EX1
+         ×  39               Also known as EX2
+
+
+
+<!-------------------------------------------------------------------->
+[Backplane]: ./RC6502%20Backplane/