HP 2500C Series - Manual (Page 148)

Functional Overview 6-28
Firmware
Interface with mechanism
The following diagram shows the interface between the firmware and the hardware :
(hardware-firmware interface diagram)
§ Paper Motor control is an open-looped control. The firmware does not know the exact
position or the size of the paper and relies on the OOPs flag to confirm the presence
of paper.
§ Service Station control is also an open-looped control. There is no feedback to the
firmware from the Service Station.
§ Carriage Control is a closed-loop control. The Carriage PCA is enabled by the
encoder strip to read and send data back to the firmware.
§ Pen information is also controlled by a closed loop. The firmware is therefore able to
receives printing data such as pen firing parameters, pen ID and pen temperature from
the active pen.