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Expansion Bus
Reference – 34 EPM-4 Reference Manual
Expansion Bus
The EPM-4 will accept up to eight expansion modules, up to four of which can be PC/104-Plus
(PCI) expansion modules. The EPM-4 uses 3.3V PCI signaling but is 5V tolerant.
PC/104-P
LUS (PCI BUS)
PC/104-Plus modules can be secured directly to the top or bottom of the EPM-4. Make sure to
correctly configure the "slot position" jumpers on each PC/104-Plus module appropriately.
PC/104 modules must not be positioned between the EPM-4 and any PC/104-Plus modules on
the stack.
The EPM-4 is compliant with revision 2.0 of the PC/104-Plus spec. and can support four bus
master capable PC/104-Plus modules.
The BIOS automatically allocates I/O and memory resources. However, manual PCI Interrupt
routing will be used.
PC/104
(ISA BUS)
PC/104 modules are stacked on top the EPM-4. 16-bit modules first followed by 8-bit PC/104
modules.
The ÉlanSC520 Microcontroller uses a General-Purpose (GP) bus that is implemented as the ISA
bus on the Lynx. The GP bus is similar in function to the ISA bus, but not functionally identical.
Nearly all PC/104 devices in use today will work on the Lynx without modification.
Here is a summary of the differences between a legacy ISA bus and the GP bus implementation
on the Lynx.
• Only DMA channels 5 and 6 are available to PC/104 devices
• IRQ15 is not available to PC/104 devices
• PC/104 bus devices cannot initiate bus access cycles. The ÉlanSC520 Microcontroller is
always the master of the ISA bus.
• Address pipelining is not supported.
• IOCHK, REFRESH, and NOWS signals are not supported.
• MEMR and SMEMR are tied together. MEMW and SMEMW are tied together.
For a more detailed description of the GP bus and its differences from a standard ISA bus, see
chapter 13 in the ÉlanSC520 Microcontroller User's Manual.
Note: On the EPM-4 Rev 4 and above, the pass-through PC/104 (ISA) connector is keyed
(pins B10 and C19 missing) for greater compatibility with the PC/104 standard.
See Figure 5 for details.
I/O
CONFIGURATION
PC/104–Plus Modules
No hardware configuration is necessary except to jumper the expansion module for the correct
slot number.