LM1488 and LM1489 IC's specs

LM1488 and LM1489 Specs

These two ICs are excellent for interfacing RS-232 (serial) line with TTL logics. The LM1488 (the RS-232 driver) takes in TTL level and puts out RS-232 logic at +/-12V. Thus, +5V becomes -12V (logic 1 in RS-232), and 0V becomes +12V (logic 0 in RS-232). The output (Y) is the result of a NAND gate of the two inputs (A and B). The outputs can also be connected through a 300 - 470 pF capacitor to ground for noise immunity. The pins layout of the LM1488 are as follow:

A	B	Y
1	1	0
0	X	1
X	0	1

The LM1489, the RS-232 receiver, does the exact opposite. It converts the RS-232 level back to TTL. There are 2 inputs (input signal and "response control"). The output is the result of the NAND gate between the 2 inputs. The "response control" is used to adjust "threshold and hysteresis" (whatever the hell that means), but I discover that it is generally not used, and therefore, usually unnecessary. It is often tied through a 300 - 470 pF capacitor to ground. Some people have tried ignoring them while still having good results up to 38,400 bps. The pins layout of the LM1489 are as follow:

Thanks to Steve Walz for his excellent documentation on these chips (the only useful one I can find on the net).