User's Manual

68P80801E35-B 5/1/2002 11
EBTS System Manual - Vol 2 Base Radio Controllers
Enhanced Base Radio Controller
background mode. Background mode transfers allow the station to remain
operational during new code upgrades.
The data that determines the station personality resides in a 32K x eight bit
codeplug EEPROM. The microprocessor addresses the EEPROM with 15 of the
host address bus’ 32 lines. The host accesses EEPROM data with eight of the data
bus’ 32 lines. A host-operated chip-select line provides control signals for these
transactions.
During the manufacturing process, the factory programs the codeplug’s default
data. The BRC must download field programming data from network and site
controllers. This data includes operating frequencies and output power level. The
station permits adjustment of many station parameters, but the station does not
store these adjustments. Refer to the Software Commands chapter for additional
information.
Volatile Memory
Each BRC contains 8MB x 32 bits of SDRAM. The BRC downloads station
software code into SDRAM for station use. SDRAM also provides short-term
storage for data generated and required during normal operation. SDRAM is
volatile memory. A loss of power or system reset destroys SDRAM data.
The system performs read and write operations over the Host Address and Data
buses. These operations involve column and row select lines under control of the
Host processor’s DRAM controller. The Host address bus and column row signals
sequentially refresh SDRAM memory locations.
Ethernet Interface
The Host processor’s Communications Processor Module (CPM) provides the
Local Area Network (LAN) Controller for the Ethernet Interface. The LAN
function implements the CSMA/CD access method, which supports the IEEE
802.3 10Base2 standard.
The LAN coprocessor supports all IEEE 802.3 Medium Access Control, including
the following:
❐ framing
❐ preamble generation
❐ stripping
❐ source address generation
❐ destination address checking
The PCM LAN receives commands from the CPU.
The Ethernet Serial Interface works directly with the CPM LAN to perform the
following major functions:
❐ 10 MHz transmit clock generation (obtained by dividing the 20 MHz signal
provided by on-board crystal)
❐ Manchester encoding/decoding of frames