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élanSC300 Microcontroller Evaluation Board User’s Manual
4-6
1
Programming BIOS Flash/EPROM
or Application Flash/EPROM
This section describes how to program a Flash or EPROM device located in the
BIOS sockets (U20 or U59), and the application sockets (U16, U17, U18, U19).
The following items need to be addressed:
Controlling the programming voltage for 12-V parts such as the AMD 28F020A
Enabling writes to the BIOS and application ROM sockets
Address mapping of the Flash sockets
Evaluation board jumper settings
Controlling V
PP
There is one control for the V
PP
line for
all
BIOS and application ROM
sockets (i.e., there is no way to individually control the V
PP
line for each socket).
As described in the section “Programmable General Purpose (PGP) Pins” on page
4-2, PGP0 is used to clock the flip flops that control the programming voltage to
the ROM sockets. When Data Bit 2 is set to 1, V
PP
is set to 12 V for all ROM
sockets. See “Initialization Example for Flash Programming” on page 4-8.
Enabling Writes to the BIOS and Application ROM Sockets
Writes to the BIOS sockets and application sockets need to be specifically enabled
(they are disabled by default). This is accomplished by setting to a 1 bits 6 and 5
of the élanSC300 Index 62h.
NOTE:
Accesses to the BIOS socket or application socket are ISA cycles plus the
additional ROMCS or DOSCS signal going active. No special logic has been added
to the evaluation board to stop a ROMCS or DOSCS cycle from going to the ISA
bus. Because of this, if the élanSC300 microcontroller is in Full ISA mode, an ISA
card (such as a VGA card) set up to respond to a memory range interferes with
cycles going to the application or BIOS sockets. For example, a VGA card with
on-board BIOS responds to the address range from A0000h through C7FFFh. An
access to the application ROM socket through the MMS page to an offset in this
range causes both the VGA card and the application ROM to respond. The only
way to avoid this is by either not accessing this range, or reworking the evaluation
board.