HP50g - RS-232 cable

[Garth Wilson]

Quote:Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.

RS-232 (later called EIA-232, and most lately, TIA-232-F) has been contorted in all kinds of variants, but I keep seeing "TTL-level RS-232" on many forums. That's an oxymoron, but refers to the asynchronous nature (ie, that the receiver must run its own clock, started by the received start bit's leading edge), and the order and timing of the bits. The TTL levels could just as easily be connected to RS-422 or RS-485 line drivers and receivers. "Serial port" usually refers to this common asynchronous signaling method; but there are synchronous-serial ports too which are totally incompatible. SPI and I²C are quite popular for interfacing ICs, but usually are not run long distances like RS-232 can be. Contrary to urban legend, RS-232 can go many hundreds of feet. A friend writes, "I know from application experience that 115.2Kbps is readily achievable on CAT5 UTP cable over a distance of 325 feet." RS-422 and -485 can go at least 90kbps at 3/4 mile.