Professional-DOS Version 1, PROM 82S123A

Contents of the PROM 82S123A (74S188), used as address decoder
with the following assignements (view schematic diagram):

A4 - address line A12 from 6502
A3 - address line A13 from 6502
A2 - address line A14 from 6502
A1 - address line A15 from 6502
A0 - address line A8 from 6502

O8 - Fetch 2MHz mode, enabling line to diode D1
O7 - Select-A[0..3|4..7]->AL, enabling line to IC4)
O6 - ROM-Banksel, A13 line to IC8 and enabling line to IC9
O5 - ROM-/OE, enabling line to IC8
O4 - RAM-/CS1, enabling line to IC9
O3 - /EN-AL->AH, enabling line to IC7
O2 - /EN-A[4..7]->AH, enabling line to IC5, pin 1
O1 - A13-EXT, address line A13 to 6502 adaptor (external A13)

   Address  ||  stored value
   A[43210] ||     O[87654321]
============||================
 0 | 00000  ||  61 | 00111101
 1 | 00001  ||  61 | 00111101
 2 | 00010  ||  43 | 00101011
 3 | 00011  || 107 | 01101011
 4 | 00100  ||  61 | 00111101
 5 | 00101  ||  61 | 00111101
 6 | 00110  ||  60 | 00111100
 7 | 00111  ||  60 | 00111100
 8 | 01000  ||  61 | 00111101
 9 | 01001  ||  61 | 00111101
10 | 01010  ||  53 | 00110101
11 | 01011  ||  53 | 00110101
12 | 01100  ||  61 | 00111101
13 | 01101  ||  61 | 00111101
14 | 01110  ||  13 | 00001101
15 | 01111  ||  13 | 00001101
16 | 10000  ||  61 | 00111101
17 | 10001  ||  61 | 00111101
18 | 10010  ||  45 | 00101101
19 | 10011  ||  45 | 00101101
20 | 10100  ||  61 | 00111101
21 | 10101  ||  61 | 00111101
22 | 10110  ||  60 | 00111100
23 | 10111  ||  60 | 00111100
24 | 11000  ||  61 | 00111101
25 | 11001  ||  61 | 00111101
26 | 11010  ||  53 | 00110101
27 | 11011  ||  53 | 00110101
28 | 11100  ||  61 | 00111101
29 | 11101  ||  61 | 00111101
30 | 11110  ||  13 | 00001101
31 | 11111  || 141 | 10001101