Panasonic KX-B620 - Page 54

KX-B620 Series
KX-B520 Series
2) Circuit Operation ,
There are 27 driver !Cs aligned horizontally on the thermal head and each one of these ICs can drive
64 heat emitting resistors.
This means that one line is at a density of 64X27=1,728 dots = (8 dots//“mm).
White “ Black (white = 0, black = 1) data in one line increments is synchronized at 1C103 pin 22
(CLKHD) and sent from 1C103 pin 21 (HDATA) to the shift register. The shift registers of the 27 ICs
are connected in series, and upon shift of 1,728 dots increment, all the shift registers become filled
with data, and a latch pulse is emitted to each IC from 1C102 pin 35 (LATCH). With this latch pulse
all the contents of shift registers are latched to the latch registers. Thereafter, through the addition
of a strobe from 1C103 only the dot location for black (= 1) among latched data activates driver, and
current passes to heat emitting body to cause heat emission. Here the strobe of STB1 to STB4
impresses 0.84 or 0.91 msec each, two times for one line printout. The sequence is as shown below.
CONTROL BOARD ' THERMAL HEAD
LATCH
1728 BIT SHIFT REGISTER
Equivalent Circuit
=-_-_-__—
HS 840 nS
Fig. 31 Timing Chart