•
PAIR SHORTED
1/2
3/4
5/6
7/8
9/10
11/12
13/14
BIT CLEARED
A9
A8
A7
A6
A5
A4
A3
•
•
956 Manual
August 1994
Within a given jumper group, the individual jumpers set the values of individual I/O base address bits,
as shown in Table 3-6. Shorting a particular jumper pin pair sets the corresponding address bit to 0.
Table 3-6. I / O Address Selection Jumper Pins
As the table indicates, the jumpers set values for the upper 7 bits of a 10-bit address (since the base
address must be on 8-byte boundaries, the last three bits are 0). To determine which jumpers to short,
write the three hex characters of the desired address, convert each to binary, ignore the two leading
zeros and the last three zeros, and then install jumpers to short the pin pairs corresponding to the
remaining zeros in the address.
As an example, suppose that you want to assign base I/O address 02E8h. Converted to binary, this
would be 0010 1110 1000. Bits A8 and A4 are zeros, therefore, you would short pin pairs 3/4 and
11/12, leaving all the other pairs open. Usually, the SSP will be used in addition to the XVME PC/AT
serial and parallel ports. Hence, Xycom recommends COMA be set to I/O port 03E8, (see Table 3-4),
COMB to 02E8 and the parallel port to 0278, (see Table 3-7, on the following page).
3-5
