61
The Socket SSD memory can be read anytime. It can be written as well, but a Write Enable
line, controlled by software, must be asserted first. Writes are ignored when the Write
Enable Line is de-asserted. This is useful to protect the contents of the SSD from being
compromised by errant programs.
The Write Enable line for the Socket SSD is bit 5 of it's Page Selection Register. A value
of "1" enables writes, a value "0" disables writes.
7
6
5
4
3
2
1
0
S o c k e t S S D P a g e S e lec t i o n R e g i s t e r
B it
1 6 K P a g e N u m b e r
0: Socket SSD Writes Disabled
1: Socket SSD Writes Enabled
14. 3 Factory SSD Configuration
The Factory SSD consists of one or two Flash memory devices soldered on the board. The
devices can be 1M or 2M individually, resulting in SSD capacities of 1M, 2M, or 4M. Like
the Socket SSD, the memory of the Factory SSD is accessible in a window in the Upper
Memory Area. Jumpers E5 and E6 control the size and base address of the window.
E5
E6
Window Size
Window Address Range
In
In
16K
D8000 - DBFFF
In
Out
16K
EC000 - EFFFF
Out
In
64K
E0000 - EFFFF
Out
Out
NA
Disable Factory SSD
14.3.1 Factory SSD Page Selection
The Factory SSD memory is divided into 256 16K Page Units. Page selection is
accomplished using Custom Register 3 of the Custom Feature I/O. Bits 0 through 7 of
Register 3 select one of the 16K pages for access in the Factory SSD Window. For a
Window size of 64K, the two low order bits are ignored.
