Canon image Prograf iPF780 Series, Service Manual

Page: 63 / 326

Chapter 2
2-4
2. Print drive timing
Each printhead houses 12 trains of nozzles, which share the same data transfer clock (Hx-CLK) and data latch pulses (Hx-LT).
Even-numbered nozzle data (Hx-x-DATA-x-EV), odd-numbered nozzle data (Hx-x-DATA-x-OD) and the Heat Enable (Hx-x-HE-x) signal are generated for each
nozzle train and controlled individually.
Printing is carried out in two ways through reciprocating motion of the carriage.
An encoder sensor mounted on the carriage generates a 150-dpi-pitched linear scale detection signal (ENCODER_A) and a signal (ENCODER_B) shifted 120 de-
grees in phase. The direction of carriage motion is detected from the status of the ENCODER_B signal relative to the leading edge of the ENCODER_A signal.
The printhead is driven using a 2400-dpi timing signal (internal signal), which is generated by dividing the ENCODER_A signal detected at the 150 dpi timing into
16 equal sections.
Printing in the forward direction is triggered at the leading edge of the detection signal (ENCODER_A).
Printing in the backward direction is carried out the same way as printing in the forward direction but at the trailing edge of the detection signal (ENCODER_A),
when the order of heated nozzles is reversed depending on the sequence of transfer of even-numbered nozzle data and odd-numbered nozzle data.
F-2-4
150dpi
2400dpi
Internal signal
2400dpi
Low active
Linear scale
Data of block 0
Data of block 0
Data of block 0
Data of block 0
Data of block 2
Data of block 2
Data of block 2
Data of block 2
Data of block 4
Data of block 4
Data of block 4
Data of block 4
Data of block 22
Data of block 22
Data of block 22
Data of block 22
ENCODER_A
ENCODER_B
H0_CLK
H0_A_DATA_0_EV
H0_A_DATA_1_EV
H0_LT
H0_A_HE_1
H0_A_DATA_0_OD
H0_A_DATA_1_OD