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4.9
SYSTEM CLOCK CIRCUIT
In order to acquire speed to transfer data to Head, input 16MHz clock in CLK16M pin (Pin 93.) Divide this clock
internally into four to create 4MHz, which is used as the basic clock for data transfer. As this clock serves as the
basic clock for data transfer, clock frequency which can assure enough pre-pulse /main pulse data transfer for the
printing period is needed.
4.10 HEAD VOLTAGE INTERRUPTING CIRCUIT
HVC pin (No. 4 pin) is used to prevent, by not applying Vh voltage to Head unless Thermal Head is in use, erroneous
printing (on resetting, etc.) and electrolytic etching. This is also used on detection of Head break-off as described in the
next section. Without use of this pin, Head Break-Off Detecting Circuit can neither be used.
For printing, after print data are transferred to Head, Head voltage is applied to Head through use of this pin. On
completion of printing, Head voltage is interrupted to be made in standby state.
On detection of Head break-off, it is held interrupted so that Head voltage (Vh) is not applied to Thermal Head.
HVC pin and HVC bit of Head Control Mode Register are synchronized. With Head Control Mode Register bit being
set and cleared, the pin also changes syncronized.
4.11 HEAD BREAK-OFF DETECTING CIRCUIT
HRCHK pin (No 5pin) is used for measurement of Thermal Head resistance value. With this pin being used while
Vh voltage of Thermal Head is held
interrupted by the above Head Voltage Interrupting Circuit, Vdd is applied to Thermal Head. In measurement,
voltage is read where Vdd voltage has been divided into Head resistance value and the reference fixed resistance.
Measurement is conducted by one time on supply of power and the detecting circuit is held in OFF afterwards.
HRCHK pin and HRCHK bit of Head Control Mode Register are synchronized. With Head Control Mode Register bit
being set and cleared, the pin changes being alos synchronized.
Measuring Procedures:
1.
Thermal Had buffer is cleared according to the print data transfer procedures. ("00h" is written in by 1-dot
line.)
2.
Set Head voltage Vp to off by using HVC pin.
3.
Supply, by HRCHK pin, Vdd voltage to Thermal Head.
4.
Writing 01h by 1 byte to Thermal Head, set the data so that only the dot among all the other dots is printed.
5.
Latch print data to Head by LATCH signal.
6.
Supply STB to Thermal Head. (Control, at this time, current supply time so that Head does not actually print
on paper.)
7.
Calculating resistance value of the heating element by using the partial pressure rate of the heating element
resistance value and the reference resistance value of Head, see if there is any "drift."
8.
Then, by performing one-shot output in HRCLK (bit 3) of Head Control Mode Register, shift the print data by
one dot.
9.
Supplying current again to Head, carry out measurement of heating element resistance value.
10. By repeating the above by the number of heating elements, you can inspect all the dots.
15
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