The EXTMEM pin enables or disables the optional EEPROM interface. When the EXTMEM pin is high, the product ID (PID) displayed during enumeration is the general-purpose USB hub. For this default, pin 5 is disabled and pin 6 functions as the GANGED input pin. If custom product ID (PID) and vendor ID (VID) descriptors are desired, the EXTMEM pin must be low (EXTMEM = 0). For this configuration, pins 5 and 6 function as the EEPROM interface with pins 5 and 6 functioning as EECLK and EEDATA, respectively. See Table 1 for a description of the EEPROM memory map. A block diagram example of how to connect the external EEPROM if a custom PID and VID are desired is shown in Figure 8.