Lexmark X644e User Guide

The following paragraphs show acceptable values for serial communication 
parameters.

The maximum voltage level for control lines or data lines is +/- 25 positive V dc and
+/- 25 negative V dc. A timing or control line is active if the voltage is more than +3 V, 
or inactive if the voltage is less than -3 V. The voltage reference point is the signal 
ground on pin 7.

A data signal greater than +3 V means that the bit is a logical 0. A signal less than
-3 V means that the bit is logical 1.

For additional information, refer to Interface between Data Terminal Equipment and 
Data Communications Equipment Employing Serial Binary Data Interchange, 
published by the Electronic Industries Association, publications EIA RS-232C and 
EIA\TIA-232-E.

The computer sends serial data in data frames (also known as packets). You can 
create 10-bit, 11-bit, and 12-bit data frames and set the serial data transfer parameter 
so that each data frame contains 7 or 8 data bits. However, your printer is an 8-bit 
printer; characters, controls, and all points addressable (APA) graphics need 8 bits of 
data. If you select 7-bit data transfer, some unexpected characters might print.

The list of acceptable data transfer rates (in bits per second) can be accessed from 
the printer operator panel or through MarkVision Professional. See your printer 
documentation for more information.

The printer sends or receives 7 or 8 data bits in each transmission frame, depending 
on which one is selected.