The signal assignments for the PC/104 interface is shown below.
This version of the standard carriers both the XT and AT signals.
However cards don't have to carry both sets of signals, and cards without a J1 or J2 may be found.
This is a stacked interface, so a card not carrying a group of signals could not be placed between cards that do.
Having a card not carrying one or the other signal groups limits its application, as it could only be used at the top of a stack.
There's another version of the standard that drops the older XT signals, by removing the signals from the interface standard.
The longer connector near the card edge is the XT connector, and the shorter connector in-board is for AT signals.
|Number||Row A||Row B||Row C1||Row D1|
|20||SA11||SYSCLK||Not Used||Not Used|
The specification defines the new mechanical
foot print and card power requirements.
PC-104 uses the PC/PCAT card specification (IEEE P996), but changes the form factor.
This is a stacked bus with no backplane or interconnecting cable. The cards plug into each other.
A PC-104 card may use an 8 bit interface (PC) or 16 bit interface (PCAT).
The PC104 bus is AC terminated to reduce power.
An additional enhancement termed PC/104-Plus allows the addition of the PCI bus onto the card.
The PC-104 Bus pinouts shown above use the same pinout described in the PC-AT bus. PC-104 is the PC-AT bus in a new form factor [Card size].
The XT bus used a 62 pin connector in the PC and also with the PC-104 bus. The XT bus is used on J1 in the PC-104 bus, shown above [Also J1 on the PC card].
The AT bus used a 38 pin connector in the PC and also with the PC-104 bus. The AT bus is used on J2 in the PC-104 bus, shown above [Also J2 on the PC card].
Both J1 and J2 Connector used with the PC104 bus have .100" spacing, and are produced in two versions.
The connectors may be 'stack-through' (pins extend out the other side of the PWB), or 'non-stack-through' (normal PWB mounting).
Return to the main PC104 bus page for a description, connector manufacturers, IC manufacturers and links.
PC-104Plus adds an additional connector; J3 which carries the PCI bus signals.
Refer to the PCI-104 pinout page, or PCI Bus page for a bus description and information.
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