QUANTUN QP-750 Service Manual
Also see for QP-750: User manual
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Contents
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QP-750 Service Manual- 25 -Circuit in this section is mainly comprised of MCU, EEPROM etc.MCU control circuit accomplishes the following functions: accomplish the reset initializationaccording to the programmed feature of the radio when power on; detect keying signal and monitorbattery voltage; send necessary frequency data to PLL according to encode of the channel; switchand control transmit/receive according to the signal input from PTT; turn on/off the mute circuitaccording to the input signaling decode signal and squelch level signal; output control signal tocontrol the light/off of LED; control signaling process IC to perform tasks.`6.2.1 Memory UsageRadio operation is controlled by software that is stored in RAM located within the microprocessor(IC2506).Radio parameters and customer specific information is stored in external EEPROM (IC2501). Theoperating status of the radio is maintained in RAM located within the microprocessor. When theradio is turned off, the operating status of the radio is written to EEPROM before operating voltageis removed from the microprocessor.6.2.2 Control and Indicator InterfacePorts P24 and P25 are outputs which control the top-mounted LED indicator. When P25 is high,the indicator is red. When P24 is high, the indicator is green. When both are high, the indicator isamber when both are low, the indicator is off.Pressing the side-mounted PTT button (K1507) provides a low to port P02 (IC2506 pin 84), whichindicates PTT is asserted. Side-mounted option buttons FK1 and FK2 (K1506 and K1504) areconnected to Ports P01 (pin 85) and P00 (pin 86), respectively.6.2.3 Interface to ProgrammingThe radio can be programmed, or the programmed information can be read, using a computer withProgramming Software connected to the radio via a Programming Cable. Connection to the radio ismade via the microphone connector (part of accessory connector J1401ćJ1402).The programmingcontact (J1402 pin 2) to ports PD0_RXD (data into Up, pin 30) and contact (J1401 pin2) to portsPD1_TXD (data out of Up, pin 29).6.2.4 Storage of Customer-Specific InformationInformation that has been programmed using Programming Software, such as channel frequenciesor selective signaling codes, are stored in the external EEPROM, where it is retained permanently(unless reprogrammed) without needing DC power applied to the microprocessor. |
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