Logic Design; Gustav; Circuit Description; Rom - Ericsson EF738 Service Manual

Technical Description

Logic Design

GUSTAV

GUSTAV is a uP ASIC that consists of 15 blocks:
• 6303

• ROM

• RAM

• Bus Interface

• Decoder
• Serial Interface
• External Ports
• Watchdog On/Off
• IFC
• BAR
• Clock Generator
• Internal Ports
• Modem
• Baud Clock
• I2C Controller

Circuit Description

6303
The processor is an 8 bit processor with an asynchronous full duplex serial commu-
nication interface, DTMS/DFMS, for external connections.
ROM
There is an internal 512 byte ROM in GUSTAV which holds a Primitive Interface
Program, used for code loading into the RAM. After a reset, the CPU will begin
executing the code in IROM. If the SERV line is high, the ROM code continues to
execute, otherwise the program code in the external EPROM is started.
RAM
There are 6016 bytes of RAM available in GUSTAV. The processor uses this mem-
ory as working space when the phone is turned on. When turned off, data that has to
be saved will be stored in the EEPROM before turn off.
Bus Interface
The bus interface will provide the data and address lines to the external Flash
EPROM and will also handle the internal busses in GUSTAV.
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