RS-232 has been standard for so long that the circuits needed to control a serial port became very cheap and often exist on a single chip, sometimes also with circuitry for a parallel port.
RS-232 bol štandard pokiaľ obvody potrebovali kontrolu, sériový port sa stal veľmi lacným a často existoval ako jediný čip, niekedy tiež v prepojení s paralelným portom.