Service manual

16 TTPM3 - Service Manual March 2009
3.3 Control board
See Figure 12. TTPM3 functional block diagram on page 19 and the logic diagram
in Chapter 5.
3.3.1 Microprocessor system
The main parts of the microprocessor system are
80C420 processor
2MB FlashPROM
128 K RAM
Two programmable I/O ports
3.3.2 Memory
The Flash stores system parameters, fonts and firmware. The RAM stores print
data saved in a page memory area that can be further split into one area for fixed,
recurring, information and one area for variable information. The content of the
RAM is deleted when power is turned off while the data in the Flash remains.
3.3.3 Printing
The printhead has 384 heating elements in a single line. This corresponds to 48
bytes of print data per dot line. The printhead has its own CPU-like logic circuitry
with a separate 4 MHz oscillator. Data to be printed is transferred on the data bus
to the printhead, where the data is shifted byte-wise into a 48-byte wide register
before a dot line is printed.
The thermal coating on the document changes from white to black color at a spe-
cific temperature. The warmer the printhead, the less heating energy is needed and
vice versa. Therefore, the printhead contains a thermistor connected to a voltage
controlled oscillator (U11) on the control board. The frequency of the output signal
TEMP is proportional to the printhead temperature. The microprocessor uses the
TEMP signal to set the duty cycle of the regulated voltage applied to the heating
elements.
3.3.4 Magnetic stripe encoding and reading
The magnetic stripe module encodes and reads ISO tracks 1, 2 and 3 with low or
high coercivity. A center track magnetic module is also available, but the
electronics is the same with the recording and reading heads connected to track 2.
The module is connected to the control board through connector J3.
Data write and enable signals are transferred to the magnetic stripe module
through the I/O port (U5).
Read clock signals (MCRCLK1, MCRCLK2) and data signals (MCRDATA1,
MCRDATA2) are transferred directly to the microprocessor (U2), the clock signals
as interrupts.
The setting of parameter 3 affects the magnetic stripe function as follows:
n3 1 = Disable read-after-write.
0 = Enable read-after-write.