PC104P-SIO4BX User Manual, Revision: 0
General Standards Corporation
8302A Whitesburg Drive Huntsville, AL 35802, Phone: (256) 880-8787
5.1
Board ID Jumper <JP1>
Jumper JP1 allows the user to set the Board ID in the GSC Board Status Register (See Section 2.1.3). This is useful
to uniquely identify a board if more than one SIO4BX card is in a system. When the Board ID jumper is installed, it
will read ‘0’ in the Board Status Register. The Board Status Register bit will report ‘1’ when the jumper is removed.
Refer to Figure 5.1-1 for Jumper JP1 location on the back of the PCB assembly.
JP1 Jumper
Description
Notes
1 - 2
Board ID 0
Defines Board ID 0 In Board Status Register
3 - 4
Board ID 1
Defines Board ID 1 In Board Status Register
5.2
PC104P / PCI104 Slot Select Switch <U4>
The device identification and interrupt lines are controlled by the position of the selection switch U4
located at one edge of the module. The selection switch allows the board to be configured as one of four unique
devices in a PC104-Plus stack. Positions 0 through 3 provide four unique bus-access configurations, while
positions 4 through 7 are unused. The table below shows the PCI signal; connections for each slot position.
In the PC104-Plus stacking configuration, each of up to four modules is assigned specific communication signals
as described in Paragraph 3.2.2 of the PC/104-Plus specification, Version 1.2. The exact relationship or mapping of
switch positions and slot-specific signals may vary among manufacturers of PC104-Plus motherboards.
Switch Position PCI_INTx# PCI_CLKx PCI_IDSELx
PCI_REQx# PCI_GNTx#
0
PCI_INTA# PCI_CLK0
PCI_IDSEL0
PCI_REQ0#
PCI_GNT0#
1
PCI_INTB#
PCI_CLK1
PCI_IDSEL1
PCI_REQ1#
PCI_GNT1#
2
PCI_INTC#
PCI_CLK2
PCI_IDSEL2
PCI_REQ2#
PCI_GNT2#
3
PCI_INTD# PCI_CLK3
PCI_IDSEL3
PCI_REQ2#
PCI_GNT2#
4-7
X
X
X
X
X
5.3
RS485/RS422 Termination Resistors
The RS485/RS422 cable interface requires termination of the high speed differential signals to match the cable
impedance. All terminations on the SIO4BX board are a parallel termination (between the + and – signals on the
cable).
The SIO4BX transceivers have built in termination resistors of 120
Ω
on the high speed receiver signals - RxC,
RxD, RxAuxC, and DCD. If desired, the internal termination resistors may be disabled by setting D30 in the Pin
Source Register.
If desired, external termination resistors may be installed on the all signals. The on-board external termination
resistors are socketed so they can be changed or removed as necessary Reasons for changing resistors would include
the need for a different termination value, termination required on low speed signals (RTS/CTS), or the requirement
for different termination scheme. . There are four external termination resistors – RP101-RP104. The termination
resistors are standard 16-pin isolated resistor DIPs (eight resistors per DIP). Refer to Figure 5.1-1 for resistor pack
locations.
