Toshiba e-studio550 Service Manual page 304

(9) Conversion circuit for D-A
This is a circuit of the D-A converter to converse the digital signal from CPU to the analog signal.
Controls of CPU are done by the serial communications of each DI, CLK, LD signal. The analog output
signals from Ao1 to Ao4 are used to adjust the light intensity of the light emitting diode (LED) of the
reflective sensor. Also, Ao5 and Ao6 output 5V or 0V and are used as the output ports.
(10) Analog multiplexer circuit
This is a circuit to connect to COM with one of the four analog input signals. As following table shows,
the digital signals input into IC7-11pin(A), IC7-10pin(B) and IC7-9pin(C) switch the corresponding
channels and IC7-3pin(COM) at a high speed, and they are input into the A-D input terminal of CPU.
Each channel signal is an analog output signal of the reflective sensor and used to adjust the sensor
automatically.
JUNE 2002 © TOSHIBA TEC
C B A Corresponding Channel
L L L
L L H
L H L
L H H
16 - 67
0
1
2
3
e-STUDIO550/650/810 RADF