26 Maintenance Manual
4.4.2.4 Daughterboard schematic (061-0171-0x)
Page 3: MIC_1A, MIC_1B, MIC_2A and MIC_2B arrive on J5 pins 1, 2, 3 and 4.
Page 4: MIC_1A, MIC_1B, MIC_2A and MIC_2B are all connected to U7-A and
U7-B. This part connects one of the microphone signals to ChanA, and
another one to ChanB. U8-A, U12-A and associated components are the
ChanA 24dB prescaler. R35, R36, U12-B and U8-B are the ChanA 12dB
attenuator. U12-C, U11-A and associated components are the ChanA ANSI
speech filter. U11-B and associated components are the ChanA 16KHz Anti
Alias filter. The ChanB signal is handled by the same circuits as described
for ChanA and are shown below the ChanA circuits on the schematic. The
signals are now renamed MIC_OUT_A and MIC_OUT_B. U28 is a serial to
parallel output shift register that the microcontroller U1 uses to control the
multiplexer, the prescalers, and the Speech Filters on this page. The sig-
nals on U28 called SPIMOSI, SPICLK, SPICSL come from the SPI Buss on
the microcontroller U1-A on page 1.
Page 3: MIC_OUT_A is connected to U10-B pin 1 and MIC_OUT_B is connected
to U10-A pin 13. These parts are used to select whether the measurement
microphone, or the line input for each channel, will be sent to the inputs
to the Codec on the SBC. The selected input signals are then sent to the
SBC via J3 pins 6 and 2. The control signals MIC/LINE_A and MIC/LINE_B
come from U1-A on page 1.
Page 1: U1-A pins 23 and 24 supply the two MIC_LINE multiplexers on page 3
control signals. U1-A pins 39, 40, 46 are the SPI Buss which is sent to U28
on page 4.
4.4.3 SBC to Microcontroller Digital Communication Interface
4.4.3.1 Daughterboard schematic (061-0171-0x)
Page 2: J4 plugs into the PC104 connector on the SBC. U5 decodes the port ad-
dresses used by the UARTS on this page. U5 also takes the interrupt re-
quests from the UARTs, assigns them to a PC104 interrupt, and drives them
onto the PC104 buss. U5 also drives the chip select lines on the UARTS
on this page. U6 is the dual UART that communicates with the external
modules. U2 and U18 are the RS232 transceivers that drive and receive the
lines that go to the external modules. U17 is a single UART that communi-
cates with the Daughterboard microcontroller on page 1.
Page 1: U1-A RTS, CTS, SOUT and SIN lines (pins 48, 47, 49, 50) connect to the
UART on page 2. The DTR3 line goes to the Boot circuit composed of R4,
R5, R6, R7 and C3. The boot circuit then drives the U1-A reset input and
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