My answer to Is MAX232 chip compatible for any type of 8051 microcontroller? Or any specific IC are present?
Answer by Shaunak Agastya Vyas:
Yes, MAX232 is compatible for 8051 family.
MAX232 works on 5 V. All 8051 Controllers work at 5 V. The prime goal of MAX232 is to convert TTL level of Controller to RS-232 level.