The descriptions of the pins are listed in Table 7-1.TABLE 7-1: PIN FUNCTION TABLE7.1 A0, A1, A2 Chip Address InputsThe A0, A1, A2 inputs are used by the 24XX64 for mul-tiple device operation.
The levels on these inputs arecompared with the corresponding bits in the slaveaddress.
The chip is selected if the compare is true.Up to eight devices may be connected to the same busby using different chip select bit combinations. Theseinputs must be connected to either VCC or VSS.
7.2 Serial Data (SDA)This is a bi-directional pin used to transfer addressesand data into and data out of the device. It is an open-drain terminal, therefore, the SDA bus requires a pull-up resistor to VCC (typical 10 k? for 100 kHz, 2 k? for400 kHz)For normal data transfer SDA is allowed to change onlyduring SCL low.
Changes during SCL high arereserved for indicating the START and STOP condi-tions.7.3 Serial Clock (SCL)This input is used to synchronize the data transfer fromand to the device.7.4 Write Protect (WP)This pin can be connected to either VSS, VCC or leftfloating.
An internal pull-down resistor on this pin willkeep the device in the unprotected state if left floating.If tied to VSS or left floating, normal memory operationis enabled (read/write the entire memory 0000-1FFF).If tied to VCC, WRITE operations are inhibited. Readoperations are not affected.