Brother P-touch BB4, Service Manual

Page: 51 / 66

III - 8
3.2.6 Thermal Head Drive Circuit
Figure 3.2-8 shows the thermal head drive circuit.
The thermal head has an integrated heat generator (consisting of 64 heating elements
vertically aligned in 180 dpi) and a built-in driver IC.
Synchronizing with the clock on SBT0, the CPU outputs print data on SBO0 in serial form.
One issue contains a total of 64 dots, 8 sets of 8-bit data.
Figure 3.2-8 Thermal Head Drive Circuit
Figure 3.2-9 shows a timing chart for thermal head drive.
Figure 3.2-9 Timing Chart for Thermal Head Drive
Upon receipt of LATCH signal issued through P01, the thermal head drive circuit latches
the serial data sent through SBO0 and supplies the power to the thermal head ASSY
according to the STROBE signal issued through P03.
The CPU controls the ON-time length of the thermal print head according to the V
BT
level
applied to the thermal head. If the V
BT
level is low, the CPU increases the ON-time length;
if high, the CPU decreases it.