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).
