
Functional Overview 6-27
Firmware
Physical Layer
On the physical layer, the firmware performs the following functions :
It supports IEEE 1284 (bi-directional) compatibility in Forward mode.
It is able to return extended status reports to the host computer in Nibble mode.
It identifies the Device ID.
It negotiates between various modes.
Data Link Layer
On the data link layer, the firmware will perform :
Support channeling of commands, pacing, status, device ID and print data to their
respective destination devices.
Perform limited frame checking and recovery.
Application Layer
On the application layer, the firmware’s function is to :
Control the printing, media and pen.
Configure communication status.
Provide synchronized or asynchronized status reports.
Perform limited print mechanism error recovery.
Perform low-level device commands (e.g. change ID).
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