Motorola PRO Series, Detailed Service Manual

Page: 67 / 686

Controller Circuits Section 3: 1-9
Section : 6881091C63-F
There are 8 analog-to-digital converter ports (A/D) on U0101. They are labeled within the device
block as PE0-PE7. These lines sense the voltage level ranging from 0 to 5 V 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.
For example U0101-67 is the battery voltage detect line. R0671 and R0672 form a resistor divider
on INT SWB+. With 30 kand 10 k and a voltage range of 11 V to 17 V, that A/D port would see
2.74 V to 4.24 V which would then be converted to ~140 to 217 respectively.
U0101-69 is the high reference voltage for the A/D ports on the µP. Capacitor C0101 filters the 5V
reference. If this voltage is lower than 5V the A/D readings will be incorrect. Likewise U0101-68 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 will be incorrect.
1.13 FLASH Electronically Erasable Programmable Memory (FLASH EEPROM)
The 512K Byte FLASH EEPROM (U0121) contains the radio’s operating software. This software is
common to all open architecture radios within a given model type. For example, trunking radios may
have a different version of software in the FLASH EEPROM than non-trunking radios. This is, as
opposed to the codeplug information stored in EEPROM (U0111) which could be different from one
user to another in the same company.
In normal operating mode, this memory is read-only; it cannot be written to. The memory access
signals (CE, OE and WE) are generated by the µP.
To upgrade/reprogram the FLASH software, the µP must be set in bootstrap operating mode. This is
done by pulling µP pins MODA LIR (U0101-58) and MODB VSTBY (U0101-57) to low during power
up. When accessory connector pin 18 is at ground level, diode D0151 will pull both µP pins to low.
The same can be done by a level of 12 volts on line ON OFF CONTROL from the control head.
Q0151 pulls diode D0151 and in turn both µP pins to low. Diode VR0151 prevents entering
bootstrap operating mode during normal power up.
In bootstrap operating mode the µP controls the FLASH EN OE (U0121-32) input by µP pin 86. Chip
select (U0121-30) and read or write operation (U0121-7) are controlled by µP pins 38 and 4.
The FLASH device may be reprogrammed 1,000 times without issue. It is not recommended to
reprogram the FLASH device at a temperature below 0°C.
Capacitor C0121 serves to filter out any AC noise which may ride on 5 V at U0121.
1.14 Electrically Erasable Programmable Memory (EEPROM)
The external 16 KByte EEPROM (U0111) contains additional radio operating parameters such as
operating frequency and signaling features, commonly know as the codeplug. It is also used to store
radio operating state parameters such as current mode and volume. This memory can be written to
in excess of 100,000 times and will retain the data when power is removed from the radio. The
memory access signals (SI, SO and SCK) are generated by the µP and chip select (CS) is
generated by address decoder U0141-15.