Commodore Amiga A1000, Hardware Reference Manual

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either a byte-wide register or two nibble-wide registers. If the register is nibble-wide then
it must latch the low nibble of the assigned address (at $4A) until the high nibble (at $48)
is written. This allows the following algorithm to work with either type of board:
Write the low order address nibble to offset $4A
Write the entire address byte to offset $48
Alternatively, many boards can be asked to "shut-up" (pass CONFIG-OUT and stop
responding) by writing to offset S004c of the board. A bit in the nibble at offset $0008
flags whether a board supports shut-up.
All commercial expansion slot boards for the Amiga must implement the AUTOCONFIG
protocol. More in-depth machine-specific information on the design and implementation of
AUTOCONFIG boards is available from Commodore Amiga Technical Support.
The Amiga operating system contains support for matching up disk-based drivers with
AUTO-CONFIG boards. Since 1.3, the OS also supports initialisation of onboard ROM driver
software.
As a general rule, applications should not attempt to AUTOCONFIG expansion peripherals,
but rather should allow the Amiga system software to handle all automatic configuration.
Many boards contain registers which once activated could do irreparable damage, for
example, data on a user's hard disk could be lost if the board had been configured
improperly.
However, certain types of low level stand-alone applications may need to configure
hardware such as RAM boards without using the Amiga operating system. Such
applications should only configure expansion RAM boards (boards which ask to be added
to the free memory list) and known dedicated boards designed for specific applications. All
other boards should be shut-up if the board supports shut-up, or configured and ignored if
shut-up is not supported. (There are many boards which do not support shut-up).
Configuration of boards should only be attempted by applications which take over the
whole machine at reset. Presence of an AUTOCONFIG board waiting for configuration is
determined by comparing the nibbles appearing at the initial AUTOCONFIG address with
the valid values for such nibbles in the specifications.
The AUTOCONFIG spec requires that boards be configured on boundaries that match their
space requirements. For example, a 1 MB memory board should be configured on a 1 MB
boundary. There are two exceptions to this rule: boards with a 4 MB address space are
capable of being placed at S200000 and S600000 as well as being placed on 4 MB
boundaries; 8 MB boards can be placed at S200000. These exceptions are necessary
because the 8 MB space reserved for expansion in the current machine begins at
$200000.
DEBUGGING AUTOCONG BOARDS
If there is a defect in your configuration information, your board may be ignored, may
shut-up or may crash in a way that makes diagnosis difficult. There is a simple trick allows
you to test the configuration information. Cut the CONFIGIN* line to your board and wire
a switch into the line. Wire in the switch such that when it is set one way, the CONFIGIN*
line will pass through
- 336 Appendix G -