Motorola pro7100 Manuel de service Page 51

  • Télécharger
  • Ajouter à mon manuel
  • Imprimer
  • Page
    / 109
  • Table des matières
  • DEPANNAGE
  • MARQUE LIVRES
  • Noté. / 5. Basé sur avis des utilisateurs
Vue de la page 50
Theory of Operation 2-37
2.11 Control Head (PRO5100, PRO7100, CDM1250, CDM1550)
The control head contains the internal speaker, the on/off/volume knob, the microphone connector,
several buttons to operate the radio, several indicator light emitting diodes (LEDs) to inform the user
about the radio status, and a 14 character liquid crystal display (LCD) for alpha - numerical
information, e.g. channel number or call address name. To control the LEDs and the LCD, and to
communicate with the host radio the control head uses the Motorola 68HC11E9 µP.
2.11.1 Power Supplies
The power supply to the control head is taken from the host radio’s FLT A+ voltage via connector
J0801 pin 3 and the regulated +5V via connector J0801 pin 7. The voltage FLT A+ is at battery level
and is used for the LEDs, the back light and to power up the radio via on / off / volume knob. The
stabilized +5 volt is used for the µP, display, display driver, and keypad buttons. The voltage USW 5V
derived from the FLT A+ voltage and stabilized by the series combination of R0822, VR0822 is used
to buffer the internal RAM of the µP (U0831). C0822 allows the battery voltage to be disconnected
for a couple of seconds without losing RAM parameters. Dual diode D0822 prevents radio circuits
from discharging this capacitor. When the supply voltage is applied to the radio, C0822 is charged
via R0822 and D0822. To avoid that the µp enters the wrong mode when the radio is switched on
while the voltage across C0822 is still too low, the regulated 5V charge C0822 via diode D0822.
2.11.2 Power On / Off
The on/off/volume knob when pressed switches the radio’s voltage regulators on by connecting line
ON OFF CONTROL to line UNSW 5V via D0821. Additionally, 5 volts at the base of digital transistor
Q0822 informs the control head’s µP about the pressed knob. The µP asserts pin 62 and line CH
REQUEST low to hold line ON OFF CONTROL at 5 volts via Q0823 and D0821. The high line ON
OFF CONTROL also informs the host radio, that the control head’s µP wants to send data via SBEP
bus. When the radio returns a data request message, the µP informs the radio about the pressed
knob. If the radio was switched off, the radio’s µp switches it on and vice versa. If the on/off/volume
knob is pressed while the radio is on, the software detects a low state on line ON OFF SENSE, the
radio is alerted via line ON OFF CONTROL and sends a data request message. The control head µp
will inform the radio about the pressed knob and the radio’s µp switches the radio off.
2.11.3 Microprocessor Circuit
The control head uses the Motorola 68HC11E9 microprocessor (µp) (U0831) to control the LED’s
and the LCD and to communicate with the host radio. RAM and ROM are contained within the µP
itself.
The µP generates it’s clock using the oscillator inside the µP along with a 8 MHz ceramic resonator
(U0833) and R0920.
The µPs RAM is always powered to maintain parameters such as the last operating mode. This is
achieved by maintaining 5 volts at µp, pin 25. Under normal conditions, when the radio is off, USW
5V is formed by FLT A+ running to D0822. C0822 allows the battery voltage to be disconnected for a
couple of seconds without losing RAM parameters. Diode D0822 prevents radio circuits from
discharging this capacitor.
There are eight analog-to-digital converter ports (A/D) on the µp. They are labeled within the device
block as PE0-PE7. These lines sense the voltage level ranging from 0 to 5V of the input line and
convert that level to a number ranging from 0 to 255 which can be read by the software to take
appropriate action.
Pin VRH is the high reference voltage for the A/D ports on the µP. If this voltage is lower than +5V the
A/D reading is incorrect. Likewise pin VRL is the low reference for the A/D ports. This line is normally
tied to ground. If this line is not connected to ground, the A/D readings could be incorrect.
Vue de la page 50
1 2 ... 46 47 48 49 50 51 52 53 54 55 56 ... 108 109

Commentaires sur ces manuels

Pas de commentaire