Motorola MCS 2000 Service Instructions Manual page 97

Controller Section Theory of Operation: MicroprocessorOperation
The FLASH EEPROM (U0106) contains the radio's operating software. This software is common to
all radios within a given model type. For example Securenet radios may have a different version of
software in the FLASH ROM than a non-secure radio. This is, as opposed to the codeplug
information stored in EEPROM (U0100) which could be different from one user to another in the
same company. The FLASH ROM can be 256k x 8, 512k x 8, or 1M x 8. The 1M x 8 part is usually
used for SmartZone radios. The 256k x 8 cannot be used for SmartZone radios.
In normal operating mode, this memory is only read, not written to. In bootstrap mode the Vpp pin
(U0106-11) is brought to 12 V to allow the device to be written to. The memory access signals (UV
CS, OE and MEMRWB) are generated by the SLIC. To upgrade/reprogram the FLASH software, the
µP must be set in bootstrap operating mode, and the FLASH device pin (U0106-11) Vpp must be
between 11.4 and 12.6 V.
Taking diode CR0105 into account, the voltage at J0403-21 to enable FLASH programming may
range between 12.1 and 13.1 V. Resistor divider pair R0104 and R0105 set up 4.1 V on U0106-11
which reduces the chance of logic transitions on I/O3 used as a GPIO from affecting the FLASH Vpp
port. 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.
(See "Bootstrap Microprocessor Operation" on page 16
FLASH EEPROM).
Capacitor C0102 serves to filter out any AC noise which may ride on +5V at U0102, and C0107
filters out any AC noise on Vpp.
Electrically Erasable Programmable Memory (EEPROM)
The EEPROM (U0100) contains the radio's operating parameters such as operating frequency and
signalling features, commonly know as the codeplug. It is also used to store radio operating state
parameters such as current mode and volume. U0100 is a 32 Kbyte device. 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 (EE CS, OE and MEMRWB) are generated by the SLIC.
Additional EEPROM is contained in the µP (U0103). This EEPROM is used to store radio tuning and
alignment data. Like the external EEPROM this memory can be programmed multiple times and will
retain the data when power is removed from the radio.
Note: the external EEPROM plus the 512 bytes of internal EEPROM in the 68HC11F1 comprise the
complete codeplug. Most radios will have a 32k x 8 from Atmel, but some will have a Hitachi part.
The pin-out of the two EEPROM are different so they are placed on a different set of pads. See
layout for details.
Static Random Access Memory (SRAM)
The SRAM (U0101) contains temporary radio calculations or parameters that can change very
frequently, and which are generated and stored by the software during its normal operation. The
information is lost when the radio is turned off. The device allows an unlimited number of write
cycles. SRAM accesses are indicated by the CSGEN signal U101-20 (which comes from U0103-54)
going low. U0101 is commonly referred to as the external RAM as opposed to the internal RAM
which is the 1 K (1024) bytes of RAM which is part of the µP. Both RAM spaces serve the purpose.
However, the internal RAM is used for the calculated values which are accessed most often.
68P81083C20-D
for further details on reprogramming of the
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December 6, 2004