HP 600 C2184A manual Mac I/O Description

P rin t e r I n t e rf ac e I n f o rmat io n HP De s k Writ e r P rin t e rs

Mac I/O Description

HP DeskWriter printers detect and monitor which interface mode (serial or LocalTalk) is present, and automatically switch to the appropriate protocol. The printers determine if they are connected to a LocalTalk node by detecting the presence or absence of a transformer at the interface connector port. (A transformer detected at the interface connector indicates the printer is connected to an LocalTalk network.) If the mode changes while the printer is on, the printer restarts.

HP DeskWriter printers are compatible with two Macintosh serial interface modes:

RS-422-A (57.6 Kbaud)

Clocked

RS-422-A signals are modulated against an inverted copy of the modulated signal (for example RxD- and RxD+). Data communication occurs by sensing which line is more negative than the other. Sensing line polarity in respect to an inverted signal is more immune to interference and noise than to a signal compared to a common ground. The signal is also less likely to degrade over longer cable distances.

If a serial connection is made and "clocked" mode is detected, the printer switches from DTR mode (the default at power-up ) to SPP mode. The printer selects a frequency for the clocking and clocks the DTR line at that frequency.

In AppleTalk mode, the printer receives data in a synchronous serial bit stream at 230.4 K bits per second and converts the data to parallel.

N o t e	The Macintosh I/0 connector is RS-422-A compatible. It is
	not possible to use this port as an RS-232-C serial
	interface port.