Flash Electronically Erasable Programmable Memory(Flash Eeprom)1-10; Electrically Erasable Programmable Memory (Eeprom); Static Random Access Memory (Sram) - Motorola GM328 Service Manual

1-10
1.13 FLASH Electronically Erasable Programmable Memory(FLASH EEPROM)
The 512KByte 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 a non Trunking radio. 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 only read, not 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 microprocessor 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
microprocessor pins to low. The same can be done by a level of 12 volts on line ON OFF CONTROL
from the controlhead. Q0151 pulls diode D0151 and in turn both microprocessor 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 +5V 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 signalling 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.
1.15

Static Random Access Memory (SRAM)

The SRAM (U0121) 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 CS
signal U0122-20 (which comes from U0101-CSGP2) going low. U0122 is commonly referred to as
the external RAM as opposed to the internal RAM which is the 3 KBytes of RAM which is part of the
68HC11FL0. Both RAM spaces serve the purpose. However, the internal RAM is used for the
calculated values which are accessed most often.
Capacitor C0122 serves to filter out any ac noise which may ride on +5V at U0122.
Controller Circuits