Motorola P100 Series, Detailed Service Manual, Page: 37 / 336

Controller Theory of Operation: Microprocessor Circuitry 4-5
4.2.4 TX audio amplifier and 6 order 3 kHz Low-Pass filter
The TX audio signal from ASIC Pin 8 (UHF1, UHF2) or U508 Pin 4 (VHF) is linked by TX audio amp
(U502-C) to increase limiting range. The limited audio signal is adjusted to a proper level by U508
and passes through 6 order 3 kHz low pass filter (U501-A,B) before being modulated.
4.2.5 TX modulation Adjustment
TX audio signal from Pin 8 of U502-C (UHF1, UHF2) or Pin 8 of ASIC (VHF) is linked TX modulation
adjustment IC (U508). The TX modulation is tuned in the factory. If any of the TX part is replaced, the
TX modulation must be tuned using Tuner.
4.3 Microprocessor Circuitry
The microprocessor circuitry includes microprocessor (U101) and associated EEPROM.
4.3.1 Memory Usage
Radio operation is controlled by software that is stored in internal Flash ROM memory. Radio
parameters and customer specific information is stored in External EEPROM (U104). The operating
status of the radio is maintained in RAM located within the microprocessor. When the radio is turned
off, the operating status of the radio is written to EEPROM before operating voltage is removed from
the microprocessor.
4.3.2 Control and Indicator Interface
Ports Pin 35 and 36 are outputs which control the Sub-PCB mounted LED indicator. When Pin 35 is
high, the indicator is green. When Pin 36 is high, the indicator is red. When both are high, the
indicator is amber. When both are low, the indicator id is off.
Pressing the side-mounted PTT button (PB501) provides a low to port Pin 44, which indicates PTT is
asserted. Side-mounted function buttons 1 & 2 (PB502 and PB503) are connected to port Pin 21 and
Pin 32, respectively.
4.3.3 Interface to USB programming
The radio can be programmed, or the programmed information can be read, using a computer with
CPS (Customer Programming Software) connected to the radio via a USB Programming cable
(PMDN4077A). Connection to the radio is made via the microphone connector (part of accessory
connector J601). The line connects the programming connect (J601 Pin 6) to port PRG/CLONE_RX
(data into uP, Pin 34) and PRG/CLONE_TX(data out of uP, Pin 33).
4.3.4 Storage of Customer-Specific Information
Information that has been programmed using CPS, such as channel frequencies or selective
signaling codes, etc, are stored in the external EEPROM, where it is retained permanently (unless
reprogrammed) without needing DC power applied to the microprocessor.
Table 4-1. Radio Memory Requirements
Reference No. Description Size
U101 Microprocessor Flash ROM 128 Kbyte * 8
RAM 5 Kbyte * 8
U104 Serial EEPROM 8 Kbit * 8