Printronix L5020 - Manual (Page 75)

Serial Parameters (RS-232 And RS-422)
75
ENQ/ACK
The ENQ/ACK protocol enables the flow of communication to the
printer by sending a block of data, and ending the block with an
Enquiry (ENQ) signal. When the printer receives the ENQ signal, it
acknowledges the signal, thereby indicating it has received the
entire block of data.
SERIES 1, 1 CH
When you select the Series 1 with 1 Character protocol, the printer
does the following:
• When not ready to receive data (buffer 75% full), the printer
sends a buffer full response character to the host.
• When ready to receive data (buffer drops to 50% full), the
printer sends a buffer empty response character to the host.
• If the buffer ever fills completely, the printer sends a buffer full
response character to the host every time it receives a
character from the host.
• In addition, whenever the printer state changes from online to
offline (or vice-versa), the printer sends the appropriate
response character to the host.
The printer uses different response characters to represent buffer
full and buffer empty, depending on whether it is online or offline.
These response characters are listed in the following table:
With the SERIES 1, 1 CH protocol selected, if the printer receives a
Series 1 poll character from the host, the printer removes the poll
character from its input data stream and discards it.
Online State Buffer State Response Character
Online Buffer Empty CR
Buffer Full 3
Offline Buffer Empty 0
Buffer Full 2