Toshiba B-SV4D Series Manual page 14

3. ELECTRONICS
Print Head Circuit
CLK and /LAT connected to Thermal Head control clock and data latch respectively.
The TPH_EN signal controls the DC24V voltage of the Thermal Head. When TPH_EN
is "High", the Thermal Head will be separated from 24V (V
Print Head. It is used to make sure the power of Print Head is off when turning off the
printer. And the Q1 and Q2 are used to limit current of Print Head.
The /STB1 and /STB2 determines whether to heat the Thermal Head or not. The RC
charging time of U15 and 74HC123 limit the heating time of Print Head to avoid burning
the Print Head.
The DI signal sends the printer data to the Print Head.
The TM signal is the temperature/voltage sensor for Thermal Head.
The Vdet feeds back the voltage and compensates the heat time for voltage accuracy when
printing.
Stepping Motor Drive/ Protection Circuit
Connector JP8 sends the pattern as shown in table1. The status of I0 & I1 determines the
stepping motor power level, the power level pattern is shown in table2. Motor port is the
protection pin. When it is at 'LOW' level, the power of the motor system will be closed.
Power will be ON again until MOTOR pin is the pulse of 'HIGH' level. PHASE1 and
PHASE2 determine the pattern of stepping motor drive circuit. For example, the sequence
of PHASE1/PHASE2 in full step mode is 0/0 Æ 0/1 Æ 1/1 Æ 1/0.
Power Circuit
The U3 SI-8050JD converts 24Vdc to 5Vdc. And its limit current protest is 1.6A.
Parallel Interface Circuit
The Centronics interface supports one-way transmission SPP mode or ECP mode. The
Parallel Interface Circuit is for use with the externally connected personal computer
parallel interface through the Printer Cable. When PC's strobe signal comes in, the printer
responds the 'busy status' until it reads the data from parallel interface. Printer will
respond the 'error signal' to PC when it is in error status.
DD
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3.3 Main PC Board
). U21 controls protecting
EO18-33013