Section 5: Interface Specifications
Page 5-2
XL400/410e Operator’s Manual
5.3 THE RECEIVE BUFFER
The XL printers have the ability to receive a data stream from the host in one of two ways. The
receive buffer may be configured to accept one print job at a time or multiple print jobs. The
single job print buffer is generally used by software programs that wish to maintain control of the
job print queue so that it can move a high priority job in front of ones of lesser importance. The
multiple job buffer, on the other hand prints all jobs in the order they are received by the printer,
and the order of printing cannot be changed.
Single Job Buffer
The printer receives and prints one job at a time. Each job must not exceed 64K bytes.
Multi Job Buffer
The printer is able to continuously receive print jobs, compiling and printing other jobs at the
same time. It acts much like a “print buffer” to maximize the performance of the host and the
printer.
When using the RS232 Serial interface, the Multi Job Buffer uses either the Ready/Busy with
DTR (pin 20) or X-On/X-Off flow control protocols. See these sections for more details. With an
empty receiving buffer, the status of DTR is “high” (or an X-On status if using X-On/X-Off),
meaning the printer is ready to receive data. When the receive buffer is holding 62K bytes of data
(2K bytes from being full), DTR will go “low” (or an X-Off is sent) indicating the printer can no
longer receive data. This condition is called “Buffer Near Full” (see figure below).
62K
64K
0
DTR High
or
X-On
DTR Low
or
X-Off
Buffer Near Full
0
56K
64K
DTR Low
or
X-Off
DTR High
or
X-On
Buffer Available