Xycom XVME-976/202, Manual

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XVME-976 Adapter Module
4- 4-20
Control Register 2 Functions
The content of Control Register 2 provides additional device page selection
information, +12 volt Flash EPROM programming voltage control, SRAM
write protect, power fail alarm monitoring, and battery voltage monitoring.
Table 4-20 indicates the use of the various register bits.
Table 4- 20. Control Register 2 Bit Usage
Power Address Write
Enable
Flash Address
Bit 7 6 5 4 3 2 1 0
Name VB2 VB1 -PFIRQ - -WEN VPP PS3 PS2
Read/Write R R R R R/W R/W R/W R/W
Description
Bits 7, 6
(VB1-2) Battery monitor. 1= dead or missing battery. Bit 6 = battery 1 (J4), Bit 7 = battery 2 (J5).
Bits 5
(-PFIRQ) Power fail interrupt status. Zero if system ( not battery ) power falls below threshold.
Bit 4 Ampro reserved. Always set to 0.
Bit 3
(WEN) Software controlled write protect for SRAMs or Flash EPROMs. 1 is write protect, 0 is
enabled,
Bit 2
(VPP) 12 volt Flash EPROM programming voltage. Enabled (=1) by software.
Bits 0-1
(PS2, PS3) Page select. Used to select 64K byte pages from larger memory devices. PS1 and PS2
are in Control Register 1. (See Table 3-2.)