DS-101
The IXP420 CPU has 16 General Purpose Input/Output (GPIO) pins which are used to interface to external hardware. In the case of the DS-101, the GPIO pins are used to monitor the buttons, control the LEDs, connect to the RTC, IDE controller and USB 2.0 controller.
| GPIO | IXP Ball | Function | Connected to: | Configured as: | Verified? |
| GPIO[0] | Y22 | I²C SCL | RTC | Output | Yes |
| GPIO[1] | W21 | I²C SDA | RTC | Tristate | Yes |
| GPIO[2] | AC26 | Buzzer | Buzzer | Output | Yes |
| GPIO[3] | AA24 | Power LED | Power LED | Output | Yes |
| GPIO[4] | AB26 | USB Button & USB LED | USB Button/USB LED Control | Input/Output | Yes |
| GPIO[5] | Y25 | USB LED | USB LED Control | Output | Yes |
| GPIO[6] | V21 | Test? | | Input | ? |
| GPIO[7] | AA26 | Power Off | | Output | Yes |
| GPIO[8] | W23 | Power Button | | Input | Yes |
| GPIO[9] | V22 | INTC | IDE | Input | Yes |
| GPIO[10] | Y26 | INTB | USB UHCI | Input | Yes |
| GPIO[11] | W25 | INTA | USB EHCI | Input | Yes |
| GPIO[12] | W26 | Reset Button | Reset Button | Input | Yes |
| GPIO[13] | V24 | PCI Reset | | Output | Yes |
| GPIO[14] | U22 | Status LED | Status LED Control | Output | Yes |
| GPIO[15] | U25 | Status LED | Status LED Control | Output | Yes |
USB LED Control:
| GPIO[4] | GPIO[5] | Function |
| 0 | 0 | Off |
| 0 | 1 | Green Blinking |
| 1 | 0 | Green Steady |
| 1 | 1 | Off |
Status LED Control:
| GPIO[14] | GPIO[15] | Function |
| 0 | 0 | Off |
| 0 | 1 | Green Blinking |
| 1 | 0 | Orange Blinking |
| 1 | 1 | Green Steady |