THEORY OF OPERATION (ENHANCED CONTROL HEADS) 4.2 - 7
- 4-wire RS232 Interface (25-pin D-type connector)
- SB9600 Interface (25-pin D-type connector)
- SBEP Interface (10-pin Telco connector)
- 14 pin JTAG port
General
The 25-pin D-type, the 9-pin D-type connector and the 10-pin Telco connector are mounted on the
Connector Board that is screwed into the Data Expansion Head Enhanced housing. The Milan
Expansion Board is installed at expansion board position. The interconnection between the Connec-
tor Board and the Milan Expansion Board is accomplished by a 40-pin flex connector.
A 12-pin flex and a 40-pin flex achieve the connection between the Expansion Board to the main
radio chassis. A remote mount Enhanced Control Head can be connected in a remote mount config-
uration via the 10-pin Telco connector. External DCE(s) can be connected via the 25 pin and /or 9
pin D type connectors.
Circuit Description
The Data Expansion Head Enhanced Interface consists of several circuits to provide interfaces for
the MTM800 TETRA mobile radio and the "outside world".
The Expansion board has an onboard 3-Volt Regulator U501 that is driven by 5-Volt supply from the
main radio via the 12-pin flex on J1001. The supply voltage FLT_A+ is over current protected by the
2A fuse F101.
A second regulator U503 provides VAG_1 of 9.3V for the Gabel Hybrids U201. This regulator will be
shut down through Q501 when the 5V are detached
The Gabel Hybrid U201 serves to transform the audio from unbalanced to balanced in order to
reduce noise susceptibility on the remote cable.
There are several interfaces on the board but not all of them are available at the same time
The 8 wire RS232 interface consists of the MAX3238 true RS-232 transceiver (U101) that provides
the EIA/TIA-232 and V.28/V.24 communications interface. This interface can be fully accessed
through the 9-pin D-connector.
The circuit comprising ICs U401, U403 and U404 interfaces the MTM800 SPIB bus to an asynchro-
nous serial-data communication port RS232 that is the 4-wire RS232 interface (pins 2, 3, 4, 5).
U401 is a MAX3100 universal asynchronous receiver transmitter (UART) with a baud rate generator
driven by a 3.6864 MHz crystal U402.
U404 is a MAX3232 RS232 transceiver, translating the 3V logic levels to the RS232 levels.
The next interface is an SB9600 interface on the 25-pin connector (pins 8, 13, 15, 17)
(SB9600_INTERFACE). The UART chip U401 also generates the transmit/receive signals of this
interface.
The SBEP interface is provided on the 10-pin Telco remote connector. All signals necessary to con-
nect a remote mount Enhanced Control Head are routed through this connector. Those signals are
fed from the radio via the 12-pin flex (J1001). The SBEP interface is always available on the Telco
connector.
6866539D31.book Page 7 Tuesday, March 20, 2007 6:32 PM
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