3. MrX Expansion Bus K3
The MrX Interface is supplied with a built in expansion bus (K3) which allows direct access to the
signals provided by the YM2149 sound chip, should you wish to develop an add-on daughterboard.
Pinout K3
1) IOB7 Port B from YM2149
2) IOB6 Port B from YM2149
3) IOB5 Port B from YM2149
4) IOB4 Port B from YM2149
5) IOB3 Port B from YM2149
6) IOB2 Port B from YM2149
7) IOB1 Port B from YM2149
8) IOB0 Port B from YM2149
9) IOA7 Port A from YM2149
10) IOA6 Port A from YM2149
11) IOA5 Port A from YM2149
12) IOA4 Port A from YM2149
13) IOA3 Port A from YM2149
14) IOA2 Port A from YM2149
15) IOA1 Port A from YM2149
16) CHL Left channel of 3,5mm jack, behind capacitor
17) CHR Right channel of 3,5mm jack, behind capacitor
18) GND Ground
19) /CLK ZX81 clock signal 3,25 MHz
20) GND Ground
21) ANALOG_CH_C Analog Channel C directly connected to YM2149
22) ANALOG_CH_B Analog Channel B directly connected to YM2149
23) ANALOG_CH_A Analog Channel A directly connected to YM2149
24) VCC Supply current +5V
25) GAL1 Pin 15 of GAL 16V8
26) GAL2 Pin 14 of GAL 16V8
27) GAL3 Pin 13 of GAL 16V8
28) GAL4 Pin 12 of GAL 16V8
29) clock/2 1,625 MHz
30) IOA0 Port A from YM2149
Version v005 6 Date 22.05.2012
