The STK504 has five port connectors in addition to those available on STK500. These are PORTE, PORTF, PORTG, PORTH and PORTJ.
Figure 1. STK504 port connectors
Pin 1 on each connector is connected to the corresponding port at pin 0 on the AVR. Pin 8 is connected to the corresponding port at pin 7. Each port header has GND connected to pin 9 and VTG to port 10.