VULCAN Technical Manual
Detailed hardware description
© 2007 Eurotech Ltd Issue D
36
PC/104 interface
The PC/104 interface supports 8/16 bit ISA bus style signals. Add-on boards can be
used to enhance the functionality of the main board. Eurotech has an extensive range
of PC/104 compliant modules and these can be used to quickly add digital I/O,
analogue I/O, serial ports, video capture devices, PC card interfaces etc. The ISA bus
is based on the x86 architecture and is not normally associated with RISC processors.
It is necessary to modify the standard drivers if you want them to support any third
party PC/104 modules.
The PC/104 interface is implemented using a PCI bus interface of the IXP425
processor and slot B of Texas Instruments PCI1520 PCI/CardBus Bridge. Any PC/104
board that is plugged in appears in the EXCA memory or I/O window of the PCI1520
device. The PCI1520 - PCI/CardBus Bridge itself appears in the PCI memory space of
the IXP425 processor.
The PC/104 bus signals are compatible with the ISA bus electrical timing definitions.
DMA and bus mastering are not supported on VULCAN’s PC/104 interface. For details
about PC/104 interrupts, see
, page
.
The VULCAN pr5V to a PC/104 add-on board via the J8 and J10 connectors.
If a PC/104 add-on board requires a +12V supply, then +12V must be supplied to the
VULCAN power connector J9 pin 4. If -12V or -5V are required, these must be supplied
directly to the PC/104 add-on board.
All signals between the PCI1520 CardBus Controller and the PC/104 are buffered.
After powering up slot B of the PCI1520 device, it is necessary to configure the
MFUNC2 pin on PCI1520 as GP output (ISACTL_EN#) and set it low, to enable the
PC/104 buffers.
Once MFUNC2 is set low, the PC/104 bus is enabled for access. At times when the
PC/104 bus is idle, the PCI1520 slot B and the PC/104 connector are automatically
isolated by the buffers transceiver output enables being driven high.
This is illustrated in the following table:
MFUNC2 (ISACTL_EN#)
PC/104 Operation Status
0
PC/104 Buffers Enabled (default)
1
PC/104 Buffers Disabled