Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-08-27
2002-09-10
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S011000
Reexamination Certificate
active
06447092
ABSTRACT:
BACKGROUND OF THE INVENTIONS
1. Field of Inventions
The present invention relates generally to a signaling method for a pen driver circuit interface and, more specifically, to a signaling method employing a pen driver circuit to process a combination of signals including at least one signal from a signal interface in order to provide information associated with a signal line which has been eliminated from the signal interface.
2. Description of the Related Art
FIG. 1
shows a controller/driver/pen system
100
including a controller circuit
102
, a pen driver circuit
104
and a pen
106
for a printer. The system
100
includes a conventional serial interface
108
between the controller circuit
102
and the pen driver circuit
104
. The system
100
also includes a conventional signal interface
110
between the pen driver circuit
104
and the pen
106
.
Generally, the digital pen controller
102
is responsible for communicating with the analog pen driver integrated circuit (“IC”)
104
to control the InkJet pens. More specifically, the controller circuit
102
provides data and timing information to the pen driver circuit
104
to fire drops of ink. Also, the controller circuit
102
monitors the pen head temperature and pulse-warms the pen
106
if it is not warm enough to maintain acceptable print quality.
FIG. 2
shows a timing diagram
200
of the signals typically found in such systems, namely, CLOCK
202
, DATA
204
, LOAD
206
, FIRESTROBE
208
, and WARMSTROBE
210
(the names of the signals may vary, but the functions are usually the same). In this example of a typical signaling scheme, the CLOCK signal
202
is used to shift data bit-by-bit over the DATA signal
204
from the digital application-specific integrated circuit (“ASIC”)
102
to the pen driver IC
104
. A single bi-directional DATA signal
204
is shown because some status information could be returned from the pen driver IC
104
on the same line when data is not being transferred in. Some systems may have multiple DATA signals. Once all of the data bits have been shifted into an internal shift register of the pen driver IC
104
, the rising edge, for example, of the LOAD signal
206
transfers the shift register contents into an internal control register of the pen driver IC
104
. This loading step is necessary to prevent the pen driver IC
104
from responding to the shifting data as the bits trickle over each of the various control bit positions. Once the data has been transferred and loaded, firing and warming may begin.
For the sake of simplicity, the timing diagram
200
shows both the FIRESTROBE signal
208
and the WARMSTROBE signal
210
being asserted on the same transfer. This may or may not be the case. The FIRESTROBE signal
208
causes pen nozzle resistors in the pen
106
which have been selected by the transferred data to be driven with electrical current for a sufficiently long period of time to heat the resistor to a high enough temperature to fire a drop of ink. The WARMSTROBE signal
210
is used to drive current through all of the nozzle resistors, regardless of which nozzles have been selected for firing. The WARMSTROBE pulse
210
is generated for a sufficiently long period of time to heat the nozzle resistors (and therefore the pen head), but is short enough in duration to avoid firing ink out of the nozzles.
FIG. 9
is a schematic of an exemplary conventional multiplexing circuit
900
for controlling nozzles in a printhead of a printer which has sixteen (16) groups of nozzles, with four (4) nozzles in each group. The multiplexing circuit
900
includes nozzle group selection logic
902
, AND-gates
904
,
906
,
908
and
910
, OR-gates
912
,
914
,
916
and
918
, and AND-gates
920
,
922
,
924
and
926
configured as shown.
In operation, only one nozzle group is selected at a time via the four group select bits provided as inputs to the group selection logic
902
. By way of example, when group ‘n’ is selected, all four nozzles in group ‘n’ are driven whenever the “Warm Enable Pulse”
210
is asserted. If the “Warm Enable Pulse”
210
is not asserted, any of the nozzles in group ‘n’ will be driven whenever the “Fire Enable Pulse”
208
is asserted and the corresponding “Select Bits” for those nozzles are asserted. If neither the “Warm Enable Pulse”
210
or the “Fire Enable Pulse”
208
is asserted, no nozzles are driven. In logic terms, a nozzle is driven when: (its group is selected) AND ((the “Warm Enable Pulse”
210
is asserted) OR (the “Fire Enable Pulse”
208
is asserted AND the nozzle is selected)).
A drawback of the above-described signaling implementation is that five signals are required to perform all of the functions necessary to provide data shifting, data loading, and independent nozzle firing and pulse warming.
A possible solution would be to make the pen driver IC
104
more “intelligent” so that it can automatically warm and fire the pen
106
once data has been received from the digital controller
102
. Such a system could theoretically have a pen driver IC
104
with only one control signal that uses a self-clocking serial data transfer protocol to receive data from the digital controller ASIC
102
. Once all the data has arrived, the “smart” pen driver IC
104
would wait an appropriate amount of time per its programming before firing the pen
106
, and would also monitor the pen head temperature to automatically warm the pen
106
without intervention from the digital ASIC
102
. While such an approach would provides a single control signal, it requires a more complex pen driver IC
104
. Pen driver ICs are power devices designed to drive high currents at high voltages; however, they are not well suited for containing control logic. Furthermore, such a “smart” pen driver
104
would require a phased-locked loop (“PLL”) to synchronize with the data stream on the single control line since there is no dedicated clock.
Another possible solution would be to provide a two wire signal interface having just CLOCK and DATA signals. Although such a signal interface would not require a PLL, the pen driver circuit
104
would still need to automatically control the timing of the firing and warming events, which would require on-chip timers and an oscillating clock circuit on the IC
104
or on the printed circuit board (“PCB”).
In summary, the addition of a PLL and/or timers to the pen driver circuit
104
increases the complexity and cost of the pen driver IC
104
by adding circuitry that analog fabrication processes are not well suited for. Additionally, placing control of the firing and warming timing in the pen driver IC
104
could reduce flexibility, possibly making the IC
104
less desirable to be used in future products. If the pen driver IC
104
is located on a carriage printed circuit assembly (“PCA”), an oscillating clock at the carriage would also have increased radiated emissions at radio frequencies, which may require extra cost to suppress in order to satisfy regulatory requirements.
Thus, a need exists for a control interface to an InkJet pen driver IC that provides lower system cost without sacrificing functionality, namely, a pen driver IC signaling implementation which provides the full functionality and information content of a conventional control interface and reduces the number of control signals, without adding a significant amount of circuitry to the pen driver circuit.
SUMMARY OF THE INVENTIONS
A signaling method for a pen driver circuit interface in accordance with one embodiment of the present invention reduces a number of signal lines in a signal interface between a controller circuit and a pen driver circuit of a printer by employing combinations of signals including at least one signal on the signal interface to provide information associated with a signal line which has been eliminated from the signal interface. The pen driver circuit is configured to process the combination of signals to provide the information which includes, for example, firing and warming pulse signal information for controlling nozzles in a prin
Dudding Alfred E
Gordon Raquel Yvette
Hewlett--Packard Company
Potts Jerry R.
LandOfFree
Signaling method for a pen driver circuit interface does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Signaling method for a pen driver circuit interface, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Signaling method for a pen driver circuit interface will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2881657