Onboard Bios Operation; Power-Up Diagnostics - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter

Onboard BIOS Operation

A host adapter BIOS is provided to emulate the standard hard disk BIOS and boot
functions. With this BIOS, the host adapter can be used in lieu of a standard hard
disk controller on any ISA-compatible system.
The BIOS is compatible with the standard hard disk BIOS. This allows DOS to ac-
cess up to two hard disk devices on the SCSI bus without a driver. All normal I/O
functions are supported including system booting. Single-threaded operation and mul-
tithreaded operation do not operate simultaneously. Single-threaded operation can-
not be requested until all multithreaded operations are completed. Similarly, all
multithreaded operations must be complete before a single-threaded operation can be
requested. For most multitasking operating systems, such as Xenix
gle-threaded operation is normally used only for the early part of the boot operation,
after which multithreaded drivers take over all control of the SCSI operations.
During system boot, the BIOS will scan for the availability of configuration informa-
tion in the free-form data area of system RAM. If it finds the correct data format, it
will use this data to configure both the board parameters and parameters associated
with the peripherals on the SCSI bus. If data cannot be found or correctly recognized,
the BIOS will configure the board to a default set of parameters. Refer to Chapter
Three, Installation for details.

Power-Up Diagnostics

After power on, the host adapter initializes the firmware to 16-bit RAM for execution.
After the firmware is running, the Extended ID is written to the registers. Several on-
board diagnostics are then performed.
RAM is verified
Write/Read registers are checked for proper operation
The data path is checked for correct internal operation
The red Light-Emitting Diode (LED) on the host adapter indicates the result of the
self diagnostic process. When power is first applied to the board, the LED turns on. If
the board is operating normally, the light will soon go off and stay off until SCSI or
I/O port activity is requested by the host. If the board is not operating correctly, a
flash code number is flashed on the LED to indicate which test failed. The flash code
number is indicated by a series of one to three closely spaced flashes, followed by a
longer pause, or a continuous series of flashes. The flash code is repeated continu-
ously until the board is powered off or reset. The SCSI interface should be discon-
nected if these diagnostic tests are being run for fault isolation purposes. At least one
set of terminators must remain installed or the LED will stay on, indicating that the
AHA-1740A/1742A/1744 is receiving an active RST signal. The flash code and associ-
ated failure modes are indicated in the following table.
Architecture
®
and OS/2, sin-
2-11