Cartridge Port

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The Master Component's cartridge port consists of a single 44-pin 0.1" spacing edge-card connector. A number of essential bus signals are brought out on this connector. The following figures illustrate which of these signals corresponds to each of the various cartridge pins. The table afterwards lists what each signal does.

Pin Mapping on Intellivision Cartridge Port

T cart top.png T cart bot.png

Pin Assignments

Component Side (Top)   Solder Side (Bottom)
Description Name Pin Pin Name Description
Ground. GND 2 1 GND Ground.
Character BLaNK CBLNK 4 3 ~MSYNC Master SYNC.
External Audio Input. Ext. AUDIO 6 5 DB7 Bit 7 of the Address / Data Bus.
External Video Input. Ext. VIDEO 8 7 DB8 Bit 8 of the Address / Data Bus.
Master CLocK. MCLK 10 9 DB6 Bit 6 of the Address / Data Bus.
Reset input. RESET 12 11 DB9 Bit 9 of the Address / Data Bus.
Timing signal from the STIC. SR1 14 13 DB5 Bit 5 of the Address / Data Bus.
Intellivoice special purpose.  ??? 16 15 DB10 Bit 10 of the Address / Data Bus.
 ??? 18 17 DB4 Bit 4 of the Address / Data Bus.
Ground GND 20 19 DB11 Bit 11 of the Address / Data Bus.
GND 22 21 DB3 Bit 3 of the Address / Data Bus.
GND 24 23 DB12 Bit 12 of the Address / Data Bus.
GND 26 25 DB13 Bit 13 of the Address / Data Bus.
GND 28 27 DB2 Bit 2 of the Address / Data Bus.
BUS AcKnowledge. ~BUSAK 30 29 DB14 Bit 14 of the Address / Data Bus.
This is an input. This BC1 drives the EXEC ROMs, the PSG, and the 8-bit RAMs. BC1 32 31 DB1 Bit 1 of the Address / Data Bus.
This is an input. This BC2 drives the EXEC ROMs, the PSG, and the 8-bit RAMs. BC2 34 33 DB0 Bit 0 of the Address / Data Bus.
This is an input. This BDIR drives the EXEC ROMs, the PSG, and the 8-bit RAMs. BDIR 36 35 DB15 Bit 15 of the Address / Data Bus.
This is an output. This BDIR is usually looped back by the cartridge on pin 36. BDIR 38 37 BDIR This is an output. This BDIR usually provides the current bus phase to the cartridge ROMs.
This is an output. This BC2 is usually looped back by the cartridge on pin 34. BC2 40 39 BC2 This is an output. This BC2 usually provides the current bus phase to the cartridge ROMs.
This is an output. This BC1 is usually looped back by the cartridge on pin 32. BC1 42 41 BC1 This is an output. This BC1 usually provides the current bus phase to the cartridge ROMs.
Ground GND 44 43 Vcc +5v power.


The following meanings are assigned to the cartridge port signals:

  • Vcc -- +5v Power

  • GND -- Ground

  • RESET -- System Reset

    Pulling this line low will send a short reset pulse to the STIC. This will result in ~MSYNC being brought low by the STIC, thereby resetting the machine. The signal is capacitively coupled inside the Intellivision. Thus, the Intellivision will only respond to the high-to-low transition of the pulse. Holding this line low will not hold the Intellivision in reset.

  • ~MSYNC -- Master Sync

    This signal goes low for at least 10ms during Reset. It is generated by the STIC as soon as the STIC recognizes a low pulse on its RESET line.

  • MCLK -- Master Clock

    This pin provides the 3.579545MHz master clock signal that drives the Master Component.

  • BC1, BC2, BDIR -- Bus Control

    These are the bus control signals as described in the CPU sections above. The outputs on pins 38, 40, and 42 come directly from the INTAK remapping circuitry. Cartridges generally loop these signals back on pins 36, 34, and 32. The outputs on pins 37, 39, and 41 are also directly connected to the INTAK remapping circuitry, and are the signals that most Mattel cartridges use for determining the bus phaase.

  • DB0 thru DB15 -- Address/Data Bus

    This is the 16-bit multiplexed address/data bus.

  • ~BUSAK -- BUS AcKnowledge

    This signal goes low when the CPU has relinquished the bus during a DMA access by the STIC. It appears possible that external devices can access the PSG, EXEC, and 8-bit RAM during the time ~BUSAK is low, but it's unclear whether this is the case. In all likelihood, it is not the case.

  • SR1 -- STIC Timing Signal

    This signal is tied to the CPU's ~INTRM input, triggering an interrupt when the STIC goes into the vertical refresh phase.

  • CBLNK -- "Character BLaNK" / Horizontal Retrace

    Used for genlocking the Keyboard Component's TMS9927 to the Master Component's AY8900 STIC.

  • EXT AUDIO -- External Audio Input

    The Intellivoice and ECS's second Programmable Sound Generator provide audio input via this pin. I'd imagine if the Keyboard Component can generate Audio, it also provides it on this pin.

  • EXT VIDEO -- External Video Input

    This was originally designed to accept the genlocked video from the Keyboard Component. The Intellivision II changed the circuit external video output slightly to accept the non-genlocked video from the System Changer. It also moved this to a different pin.

  •  ??? -- Intellivision special purpose

    These pins are tied to ground on non-Intellivoice cartridges, and left open on Intellivoice-aware cartridges.