Xycom XVME 200, Manual

Page: 30 / 57

XVME-200/290 Manual
December, 1987
A specific register address in one of the 68230 chips can be accessed by simply
adding the specific register offset to the module base address.
For example, the
offset specified for the Port General Control Register for PI/T #2 is 41H, and if
the module base address is jumpered to 1000H,
the register can be accessed at
1041H.
Module Base Address
1000H
Register Offset
41H =
PCG Register #2
1041H
NOTE
The XVME-200/290 are an odd byte only slave, and
as such,
t h e m o d u l e w i l l n o t r e s p o n d t o e v e n
address, single-byte accesses.
However, word
accesses may be used, with the understanding that
only the odd byte of the word is used to exchange
data.
If word accesses are used, the register offsets
listed in Table 3-l would all be decremented by 1.
Figure 3-l shows a simple map of the 1K block of the short I/O address space
which is occupied by the XVME-200/290 Modules.
EVEN ODD
Base + 00H 0lH
3EH
40H
U
N
U
S
E
D
3FH
41H
7EH
80H
7FH
81H
Unused
3FEH 3FFH
Figure 3-1. Memory Map of the XVME-200 and XVME-290 Modules
3-3