Available on the three Tandy Color Computer models, also known
as the CoCo (or CoCo1), CoCo 2, and CoCo 3. 
4 PIN DIN 270° FEMALE at the computer.
| Pin | Description as Printer Port | Description as RS-232 * |
|---|---|---|
| 1 | NC - Ignored | CD - Carrier Detect |
| 2 | /READY - High when the printer is ready | DATA IN - RS-232 data |
| 3 | GROUND | GROUND |
| 4 | DATA OUT - RS-232 data | DATA OUT - RS-232 data |
- Note: The pins of connector are not always used in the manner. This port is software controlled it therefore can be reprogrammed to be used in different ways. Some of the interesting uses made of this port by after market software was as a MIDI port, control signals for a device using the joystick port to digitize video images, transmission of Amateur Radio data (Morse Code/CW, RTTY, and other digital data), and as a switch control for external devices. These additional uses most times involved use with adapters.
Pins 1 and 2 of the port are required to be inputs, due to the nature of the hardware. The software used determines in what these inputs are utilized. When used as a bidirectional RS-232 port, such as when used with a communications program, the port should be used with the stated RS-232 pin-out, the built-in BASIC printer routines use pin 2 as “printer ready” status and completely ignores Pin 1.
This port is referred to by many users and programmers of the Color Computer as the “bit-banger” port. This is due to the use of software to emulate a hardware controlled RS-232 port. Software control used valuable processor time, many added an additional hardware controlled RS-232 to eliminate use of this port or to separate printer and communications functions.