Most MS-DOS and AT-compatible computers support up to three parallel
and two serial ports, which come on expansion boards you plug into your
computer.When you installsuch boardsyoumust setswitches toindicate the
numberand addresses ofthese ports. If youspecify thewrong addresses, you
won’t be able to print.
Serial interface: rate
Ifyou ask for the Serial interface you’ll have to tell your printer more about
how thedata will be coming in —in particular its rate and unit size and the
meanings of any special bits.
The Rate parameter specifies how fast data will be arriving, measured in
baud (named afterthe French communications engineer Jean Baudot). Pick
any of the following data transfer rates:
300 baud
600 baud
1200 baud
2400 baud
4800 baud
9600 baud (thedefault)
19200 baud
38400 baud.
Roughly,one characterasecond worksout to11 baud.Ifyou’re notsure how
fast your computer will transmit, the general rule is to experiment. Try
sendingapage to print at the highest speed, and work your way down until
the printer’s output looksOK.
Serial interface: special bits
In Serialmode you’ll also have to specify if your computer sends data bits
ingroups of seven (most computers send eight, the default for abyte).
Sometimes an extra bit gets appended to make the sum of all bits in each
character alwaysodd or even; that’s called parity. Aparity bitcan help spot
transmissionerrors. If your computer sends thatextra parity bit, you’ll have
tosay whetheritproduces anevenorodd numberof “on”bits inthecharacter.
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