Accutorr Plus Service Manual - Mindray
Accutorr Plus Service Manual - Mindray
Accutorr Plus Service Manual - Mindray
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Keypad interface<br />
The keypad is made up of a 3 x 8 matrix of keys. U6 will monitor the array of 8 keys. It<br />
is pulled up and when a key is pressed, one of those lines will go low. An interrogation<br />
will commence from the MC68302 to find which key was pressed.<br />
Communication Interface<br />
The <strong>Accutorr</strong> <strong>Plus</strong> Communication module provides the communication signal interface<br />
between the LED/CPU board and the external communication interface connector. The<br />
board supports the CIS/HIS/DIAP interface via RS-232E or RS-485, providing a feed<br />
through path for the Datascope proprietary download connector (J1), the DC/DC converter<br />
(for the =12Vdc @ 100mA required for wireless telemetry), and the RS-232 driver.<br />
SpO2 Interface<br />
The SpO2 module connects to the LED/CPU module via connector J7. Power, ie., æ15V<br />
and +5V, and ground are provided by the LED/CPU module. The MC68302, interfaces<br />
with the SCC2692 of the SpO2 module through a TTL serial interface. The SpO2 module<br />
sends serial information via signal, SpO2_TXD, and receives information via signal,<br />
SpO2_RXD. The LED/CPU module can reset the SpO2 module by asserting<br />
SpO2RST*. The signal SpO2* is used to provide the LED/CPU with the systolic signal<br />
used to create the heart beat.<br />
DAC functions<br />
U22 is a dual 8 bit DAC, that interfaces to U1, MC68302. It controls the attenuation<br />
needed for the speaker driver circuitry and the amplitude of LCD drive signal, VEE, ie.,<br />
steps of 255 from 0 to -10.4 V minimum. The device is selected via the CS_IO* signal.<br />
Power to the DAC is provided by an unboard DC-DC convertor. The DAC is written to<br />
when WR_DDAC* pulses hi when CS_IO* is active low. Timing is equivalent to that<br />
discussed in section 2.3.10.<br />
Speaker Driver<br />
This function is driven by the MC68302 in two manners. One is the enable signal,<br />
TONE, and the other will attenuate the output signal in steps of 255 via the data bus,<br />
D(0..7). TONE is a 5V signal which is divided down by 26 to 200mV and buffered by<br />
U24, LM358. This signal is then attenuated by U22, AD7528, and buffered by the other<br />
half of U24. U25 is the speaker driver section and this amplifier is set for a gain of 20.<br />
LCD<br />
The LCD drive supply voltage is specified for -10.4V minimum. It can go to a maximum<br />
of 17V with respect to VDD logic supply voltage. The DAC, U22 will take +15VF as<br />
reference voltage and feed that to TL032, U23, to invert to -15V output. That is then<br />
buffered by another section of U23 and drive base of Q9. Transistor Q8 is set up as a<br />
current limiter for Q9. It monitors the current across R32. If the voltage across R32 is<br />
greater than 0.7V, ie., 21mA, then shunt drive voltage to the base of Q9 to limit the current.<br />
2-16 Revised 12/20/00<br />
<strong>Accutorr</strong> <strong>Plus</strong> <strong>Service</strong> <strong>Manual</strong><br />
Chapter 2 - Theory of Operation