Xycom XVME-976/202, Manual

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XVME-976 Adapter Module
4- 4-4
Control Register Port Address
The MEM unit has two control registers called Control Register 1 and Con-
trol Register 2. These are I/O mapped, 8-bit registers.
Register 1 selects:
Module by board number
Socket (A, B, E, or F)
Which portion of a large device will appear in the window
Register 2 controls:
Two bits for selecting pages in large devices
Device write enable
Flash EPROM (+12) volt programming voltage enable
Battery voltage and system power fail flags
The registers are accessed by writing to the Control Register Port Address,
selected by W11pins 5 and 6. Port address selection is shown in Table 4-3.
Table 4-3.
I/O Port Address Selection (W11)
Jumper Function
5/6 Open* Control Register 1 I/O address 274h, Control Register 2 I/O Address 674h
5/6 Shorted Control Register 1 I/O address 275h, Control Register 2 I/O Address 675h
*Default
Board Number (W11)
Each memory expansion module is identified by a "Board Number" from 0
to 3. A unique Board Number allows up to four expansion modules to reside
at a single I/O Port Address without bus conflicts. The Board Number is set
by jumpering W11as shown in Table 4-4. Practical considerations limit the
number of expansion modules in a system to six. There can be multiple
modules with Board Numbers 1, 2, or 3 as long as they are at different port
addresses. However, only one module in the entire system may be Board
Number 0.