Waddington's 2001 The Game Machine

Chip labeled
Mostek
3870
MK 14154N
Malaysia
2001

20 buttons: 0-9, return, MS, MR, +/-, ., +/=, -/=, x, /, CL
12-digit 7-segment VFD (actually 13-digit, but leftmost digit not used)
speaker

3870 pinout
1  XTL1
2  XTL2    avg 2.131MHz, 36% duty cycle
3  /P0-0   keyboard column and VFD digit 5
4  /P0-1   keyboard column and VFD digit 6
5  /P0-2   keyboard column and VFD digit 7
6  /P0-3   keyboard column and VFD digit 8
7  /STROBE N/C
8  /P4-0   audio circuit (see schematic)
9  /P4-1   audio circuit
10 /P4-2   audio circuit
11 /P4-3   audio circuit
12 /P4-4   audio circuit
13 /P4-5   audio circuit
14 /P4-6   audio circuit
15 /P4-7   audio circuit
16 /P0-7   VFD digit 12 (left)
17 /P0-6   keyboard column and VFD digit 11
18 /P0-5   keyboard column and VFD digit 10
19 /P0-4   keyboard column and VFD digit 9
20 GND
21 TEST    N/C
22 /P1-4   VFD digit 1 (right)
23 /P1-5   keyboard column and VFD digit 2
24 /P1-6   keyboard column and VFD digit 3
25 /P1-7   keyboard column and VFD digit 4
26 /P5-7   VFD segment A
27 /P5-6   VFD segment B
28 /P5-5   VFD segment C
29 /P5-4   VFD segment D
30 /P5-3   VFD segment E
31 /P5-2   VFD segment F
32 /P5-1   VFD segment G
33 /P5-0   VFD segment DP
34 /P1-3   keyboard row
35 /P1-2   keyboard row
36 /P1-1   N/C
37 /P1-0   N/C
38 EXT INT N/C
39 /RESET
40 Vcc


Input Matrix
     P0-5  P0-4  P0-3  P0-2  P0-1  P0-0  P1-7  P1-6  P1-5  P0-6
P1-2  MS    MR   +/-    .     +=    -=    X     /     CL   RET
P1-3  1     2     3     4     5     6     7     8     9     0