MC-10 Serial Bus

The Radio Shack TRS-80 [MC-10] used RS232 serial bus as the serial port.
If you refer to the RS232 page you'll notice that this particular interface does not use all the available pins.
The maximum cable length was determined by RS232, using a Mini-DIN 4 pin male connector.
The MC-10 bus is OBSOLETE, as the TRS-80 was obsolete by 1984.
The TRS-80 was a commercial PC used by individuals, listed here for completeness, otherwise this section covers mainstream interfaces.
This serial port happens to be the only interface I have data on for this make of computer.

MC-10 Pin Out
Pin NumberFunction
1Carrier Detect
2Receive Data
4Transmit Data


All other Apple interfaces are listed on the Apple Computer Buses page.
The IBM PC uses a different pinout for the mouse interface and different PC Buses [descriptions and pin outs].

There are no IC's or components listed because the bus is so old; but I assume they would be TTL Devices.
However, refer here for a complete listing of Component and Device Manufacturers [alphabetic listing].

This interface is obsolete and no longer being used.
The physical interface shown above as a Circular DIN connector is still valid connector and may be purchased for any other reason.
The electrical interface used basic TTL switching levels, which of course is also being used.
It's highly doubtful that is interface will be found, even in a legacy system.
It is also unlikely that a computer from the 1980's is still in use.
The Signal Assignments shown in the table in reference to the graphic of the connector are still valid, regardless of the age of the interface.
That is, once a interface standard is no longer supported or updated, no one is around to redefine the pins or specification.

Related topics; DIN Connector Manufacturers, and Round Cable Manufacturers.

Navigation > Engineering Home > Interface Buses > Cable Buses > TRS-80 Serial Port.

Editor note; To my surprise this page still gets a 100 page views this year [2011].
I'm sure it's just people clicking a link just to see what the interface is, because they have never heard about it.
Other than a few techie type hobbyist, I can't think of a reason why this computer would still be around.
It was a consumer oriented computer anyway, no way a business would be using one.
I assume it goes without saying; you should not claim to be conforming to this interface [by name].
However it would still be perfectly reasonable to use an RS232 interface over a 4 pin circular DIN connector.

PC motherboard

Distributor rolodex Electronic Components Electronic Equipment EDA CDROM Software Engineering Standards, BOB card Cabled Computer Bus Electronic Engineering Design Table Conversion DB9-to-DB25.
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Modified 12/18/11
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