The FireWire connector has six contacts, as shown in Figure 3-2. The connector pin assignments are shown in Table 3-2.
Figure 3-2 FireWire connector
![[image: ../art/iv04.gif]](../art/iv04.gif)
When the computer is on or the power adapter is connected, the power pin provides a maximum voltage of 17 V (no load) and up to 6 W power. Maximum current is 0.5 A and is controlled by an auto-resetting fuse.
Pin 2 of the 6-pin FireWire connector is ground for both power and the inner cable shield. If a 4-pin connector is used on the other end of the FireWire cable, its shell should be connected to the wire from pin 2.
The signal pairs are crossed in the cable itself so that pins 5 and 6 at one end of the cable connect with pins 3 and 4 at the other end. When transmitting, pins 3 and 4 carry data and pins 5 and 6 carry clock; when receiving, the reverse is true.