Chapter 5 - Memory Expansion Module (XVME-956/101)
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
5.3.2 C o n t r o l Register Port Address (W11)
The MEM
unit has two control registers called Control Register 1 and Control Register 2. These are
I/O mapped, 8-bit registers.
Register 1 selects:
• M o d u l e
by
board number
• S o c k e t (A, B,
E,
or F)
• W h i c h portion of a large device will appear in the window
Register 2 controls:
• T w o bits for selecting pages in large devices
• D e v i c e write enable
• F l a s h
EPROM (+12)
volt programming voltage enable
• B a t t e r y voltage and system power fail flags
The registers are accessed by writing to the Control Register Port Address, selected by W11, pins 5
and 6. Port address selection is shown in Table 5-3.
Table 5-3. I / O Port Address Selection (W11)
5.3.3 B o a r d 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. T h e Board Number is set by jumpering W 11 as shown in Table 5-4. 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.
5-4
•
•
•
