Service Manual

MM-E 2072-09333-00
2-30
2-4.8.5 SPI
The SPI comprises a serial data line, SPI_DATA, and an associated clock line, SPI_CLK. These lines
are used to communicate with other circuits, via serial/parallel converters.
Each converter also receives a load (strobe) command, which indicates when to update its outputs. The
functions of the various serial/parallel converters are described next to the circuits which are
controlled by them.
2-4.8.6 UARTs
a. U5008 includes two internal UARTs: one of them is used to communicate with the CONTROL
HEAD module, via the CH_RXD and CH_TXD lines.
b. In addition, U5008 also uses the four UARTs in U6078 to add four additional asynchronous
communication channels, identified as A, B, C, and D, which are available in the ACCESSORY
connector, J5. These channels pass through the RS-232 transceivers, U6062 and U6063.
U5008 ECLK output provides the clock signal to the UARTs, and selects the appropriate UART
in U6078 by means of chip-select lines provided by the I/O decoder U6079.
Each UART connects to the data bus lines DATA8 to DATA15, and signals U5008 that it needs
access to the bus via interrupt lines, INTA to INTB.
c. When the optional GPS receiver is installed, the B channel (RXB, TXB) is routed by the
switches U5007, U5008 to connector J8, for connection to the GPS receiver UART lines.
2-4.9 Power Supply Subsystem
LORD module uses the +5V supply voltage provided by the HI POWER module via the VCC line. In
addition, the LORD module includes a set of local regulators, which are powered from the protected
raw supply voltage line, SW_A+, also received from the HI POWER module.
These local voltage regulators are used to provide the regulated supply voltages needed by the
microcontroller (U6021), the DSP subsystem (U6097), the audio subsystem (U6098), the synthesizers
(U6024, U6025, U2004), and the IF and RF subsystem (U1106, U1107).
The 9V supply voltage generated by U1106 is used by circuits in the common parts of the IF and RF
subsystem: a separate circuit is used to generate the 9R voltage used only by the receive path circuits,
and the 9T voltage used only by the transmit path circuits.