DSP 104-plus, Reference Manual

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1.4 PC/104-PLUS AS A PC EXPANSION BUS
Users can operate the TP400 as a single board computer. If expansion is required
I/O boards can be accessed via the PC/104 and PC/104-Plus interfaces provided on
the TP400.
The PC/104 bus is a compact version of the IEEE P996 (PC and PC/AT) bus,
optimized for embedded systems applications. DSP Design and other PC/104
manufacturers offer a wide range of I/O boards that will work with the TP400, in the
same manner that a conventional PC can be enhanced by the addition of expansion
boards.
The PC/104 I/O card range includes analog and digital I/O cards, serial comms, local
area network boards and other specialist functions. DSP Design manufactures a
number of PC/104 modules and is committed to expanding this range. It is the policy
of DSP Design to introduce, where appropriate, new PC/104 I/O cards that are
software compatible with similar cards for the PC. This has the tremendous
advantage of allowing users to make use of the software that has already been
written for desktop PC cards.
The PC/104-Plus specification enhances the PC/104 specification by adding a new
120-pin connector. This connector consists of four rows of thirty pins each arranged
in a 2mm-pitch grid. It is positioned on the board edge opposite the PC/104 bus
connectors. This new connector carries the PCI bus signals, allowing the TP400 to
access high-performance PCI chips on expansion boards.
PC/104 and PC/104-Plus boards stack one on top of another, providing a compact,
rugged computer system. For details of the PC/104 bus specification and the
PC/104-Plus specification, see DSP Design’s web site.
Because the Geode GX1 may require a heatsink or fan, the TP400 must be the top
board in a stack of PC/104 boards.
1.5 THE TP400 ARCHITECTURE
The block diagram in Figure 1 shows the architecture of the TP400. The Geode GX1
processor is directly connected to the SDRAM through a 64-bit wide high-speed
memory bus. It also performs the “north bridge” functions, accessing most of the rest
of the circuitry through the PCI bus.
The CS5530A companion chip provides the south bridge functions, and implements
an ISA bus interface to the PC/104 bus and slower peripherals. The CS5530A
includes a high-speed Ultra-ATA disk interface, USB ports and motherboard
functions (timers, interrupt and DMA controllers etc).
A high-speed connection between the Geode GX1 and the CS5530A transfers
graphics and video data from the Geode GX1 to the CS5530A, which drives both
analog CRT monitors and TFT LCD displays. A PanelLink interface chip is attached
to the TFT LCD interface.
The Geode GX1 and CS5530A are also linked by the PCI bus, which goes to the
Ethernet chip and to the PC/104-Plus connector.