Printronix SL4M User Manual page 135

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ENQ/ACK. Enquiry/Acknowledge. The host controls the flow of
communication to the printer by sending a block of data and ending
the block with an Enquiry (ENQ) character. When the printer receives
the ENQ Character, it acknowledges the ENQ, thereby
acknowledging it has received the entire block of data. Status will also
be sent before the ACK. The status is as follows:
Printer State
Online
Online or Paper Motion Fault
Platen Open or Paper Out
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DTR. The printer controls the data flow by sending this hardware
signal to the host. If there is enough room in the printer buffer, the
printer will send a high signal; if the buffer is full, the printer will send a
low signal. DTR tells the host if it is safe to send more data. (If the
host sends data during an unsafe condition, data will be lost.)
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Buffer Size in K. This option configures the amount of memory allocated
for the serial port buffer. The range is 1-16 Kbytes, in 1-Kbyte increments.
The factory default is 16.
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Trickle Time. When the printer is printing data from a host and a second
job is received by the printer from a different host, Trickle Time prevents
the second host from timing out while it is waiting for its data to be printed.
In order to support this feature, the port has to be able to accept data from
the host and store it for future use.
For example, if the printer is printing a job from the serial port and then
receives a second print job from the parallel port, the data from the
parallel port will "trickle" bit by bit into the printer buffer to prevent a
timeout error from being sent back to the host connected to the parallel
port.
The selected value is the time that the printer waits before getting the next
byte of data from the host. The Trickle Time value should be less than the
host time out value, but not too much shorter or else the printer fills up its
buffer too fast.
The options are 1/4 (factory default), 1/2, 1, 2, 4, 8, and 16 seconds and
Off.
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Timeout. This is the value used by the printer to time out from the current
port and check the other selected Port Types for data to print. When the
printer has not received data from the host after a certain period of time, it
needs to time out in order to service the other ports.
The range is 1 to 60 seconds, and the factory default is 10 seconds.
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