CH Tech Quad M-module Carrier i4000 - Manual (Page 15)

i4000 - Quad M-module carrier for VMEbus
User Manual
Version: 1.2
AcQuisition Technology bv
P.O. Box 627, 5340 AP
Oss, The Netherlands
Page 15 of 25
4. VME BUS I NTERFACE
4.1. A DDRESS I NTERFACE
The i4000 can be selected to accept either short addressing, using 16-bit addresses (A16) or standard
addressing, using 24-bit addresses (A24).
When using short addressing up to 32 i4000 boards can be put in a single VMEbus system since the lower 11
address lines (A0-A10) are used internally on the i4000. If standard addressing is used, a larger address
space is available to select the board.
The memory space occupied by the i4000 is 0x800 bytes long. This memory space is equally spread across
the four modules. So each module occupies 0x200 bytes. From these 0x200 bytes address space half is used
by the interrupt controller. The address space for each module is therefore 0x100 bytes long (8 bit
addressing).
The address space of the i4000 is selectable using dip switches (SW1 and SW2) which are accessible even
when the four module slots are occupied. When a switch is “on” the corresponding address line is a logical
“zero” and when a switch is “off” the corresponding address line is “one”.
Address modifier AM4 can be used to select either standard or short memory addressing. If AM4 is “one” (the
switch is in the off position) standard addressing is selected. If AM4 is “zero” (switch on) short addressing is
selected. When using short addressing the address lines A16-A23 are don’t cares.
Figure 4 Address Selection
O f f O n
1
2
3
4
5
6
7
8
1
2
3
4
6
7
SW3
SW2
O f f A 2 3
O n A 2 2
O n A 2 1
O f f A 2 0
O n A 1 9
O n A 1 8
O n A 1 7
O n A 1 6
O n A 1 5
O n A 1 4
O n A 1 3
O n A 1 2
O f f A 1 1
O f f A M 4
E X A M P L E :
Base A
d
ress 0
x
90
0800
( s t a n d a r d a d d r e s s s p a c e )