CIRCUIT DESCRIPTION
AUDIO/LOGIC DESCRIPTION (ALL MODELS)3.3.1 MICROCONTROLLER (U101)
General
The control logic is based on an MC68HC11F1
Separate buses are used for data and memory addressing. The data bus consists of
Memory
The operating program and most of the personality information used by the microcontroller is stored in 128K x 8 Flash EPROM U108. The use of a Flash memory device allows the program to be conveniently updated using the standard programming setup and special Flash programming software. This eliminates the need to replace the microcontroller or a memory device such as an EPROM. To reprogram the Flash device, the microcontroller is placed in a special bootstrap mode by turning power on with the MODA/ MODB inputs pulled low. This is done by the RPI by applying 20 volts to the PTT pin of the microphone jack.
Radio tuning information is stored in the 512- byte EEPROM in microcontroller U101. External 4K x 8 EEPROM U102 is used in high tier and data models to store additional personality information. An EEPROM can be programmed many times, does not require a constant power supply, and retains data indefinitely.
Temporary data storage is provided by an internal 1K x 8 RAM in microcontroller U101 and by external 8K x 8 RAM U107. These devices are used as a “scratchpad” during program execution.
Reset
The microcontroller resets when power is turned on and also when the
The microcontroller resets itself automatically for 4064 clock cycles when power is applied to the VCC input.
Reset is also triggered when the transceiver is Flash programmed. A low pulse is created by C363 and R421 when the MODA/MODB inputs of the microcontroller are pulled low to initiate this program- ming. This automatically places the microcontroller in the flash programming mode. However, reset does not occur when flash programming is complete, so power must be turned off and then on again to resume normal operation.
Data Bus
A
| February 2001 |
Part No. |