LCD 16x2 I2C screen with a DS3231 I2C Clock timer only using A4/A5 ports

For a clock project I am trying to combine an LCD Screen and a Clock Module but they both have different SDA and SCL connections that connect to the A4 and A5 ports. I heard they have different I2C addresses that the arduino will send differnent things to each. Does this mean I can plug the SCL and SDA ports into a bread borad and then have it come to the arduino as one cord to the A5 and A4 ports?

There is only one port but yes it can be shared by several devices. These devices have different software addresses e.g.

#define DS1307_ADDRESS 0x68

So I can technically use a breadboard and some people said I don't need any pull up resistors with the DS3231 installed along with the any other I2C device.

Breadboards are OK for testing and enable you to get just a pair of jumpers up to A4,A5. I have never used pullups.

Thank you

These devices have different software addresses e.g.

Is this (0x68 = 0b1101000) a software address or a 7-bit device address permanently keyed in the TWI device like DS1307 during manufacturing?

When ATmega328P is programmed as slave TWI device, we set the slave address by software; this one may be termed as software address.

Is this (0x68 = 0b1101000) a software address or a 7-bit device address permanently keyed in the TWI device like DS1307 during manufacturing?

Yes for the DS1307 which has no 'address' pins.

Partially for devices such as the PCF8574 and PCF8574A IO expanders. Those chips have three 'address' pins which allow you the option of several different addresses within a certain range.

The upper four bits (out of seven) for the PCF8574 are permanently set to 0100 and the lower three bits are determined by the levels you put on the three address lines. This means that the address range is from 0b0100000 (0x20) to 0b01001111 (0x27).

The PCF8574A IC has the exact same pinout but internally its upper four bits are set to 0111. Consequently the address range for this version of the chip is 0b0111000 (0x38) to 0b0111111 (0x3F).

Don