Merlin Pinout
                              -------------

10302012 
K.Horton
----

V2.00
updated 11032012 to fix matrix pinout

The merlin is a handheld game released some time in the early 80's.  It's red
(sometimes blue) with 15 buttons, 11 LEDs, and a speaker.

Inside is a TMS1100 (marked MP3404) which contains the "brains".  There's very
little in the way of electronics.

The TMS1100's R outputs drive the 11 LEDs:

(front view, with 4 game control buttons at the bottom)

      R0
 R1   R2   R3
 R4   R5   R6
 R7   R8   R9
      R10


When that particular R output is high, that LED is on.

The keypad is a 4*4 matrix, connected like so:


       +----+  +----+  +----+  +----+
O0 o---| R0 |--| R1 |--| R2 |--| R3 |
       +----+  +----+  +----+  +----+
          |       |       |       |
       +----+  +----+  +----+  +----+
O1 o---| R4 |--| R5 |--| R6 |--| R7 |
       +----+  +----+  +----+  +----+
          |       |       |       |
       +----+  +----+  +----+  +----+
O2 o---| R8 |--| R9 |--|R10 |--| SG |
       +----+  +----+  +----+  +----+
          |       |       |       |
          |    +----+  +----+  +----+
O3 o------+----| CT |--| NG |--| HM |
          |    +----+  +----+  +----+
          |       |       |       |
          o       o       o       o
         K1      K2      K8      K4


SG = same game, CT = comp turn, NG = new game, HM = hit me

The speaker is connected to O4 through O6.  The 3 outputs are paralleled for
increased current driving capability.  They are passed thru a 220 ohm resistor
and then to the speaker, which has the other side grounded.  The software then
toggles these lines to make sounds and noises. (There is no audio generator
other than toggling it with a software delay between to make tones).

O7 is not used and is NC.

That's all there is to the hookup of the TMS1100.  Other parts include the
RC oscillator (100pf and 27K) and a simple cap/diode reset circuit and a power
switch.