User`s manual

DIGITAL-LOGIC AG MSLB-P5 Manual V0.3
PRELIMINARY 164
Code Beeps POST Routine Description
E5h Check force recovery boot
E6h Checksum BIOS ROM
E7h Go to BIOS
E8h Set Huge Segment
E9h Initialize Multi Processor
EAh Initialilze OEM special code
EBh Initialize PIC and DMA
ECh Initialize Memory type
EDh Initialize Memory size
EEh Shadow Boot Block
EFh System memory test
F0h Initialize interrupt vectors
F1h Initialize Run Time Clock
F2h Initialize video
F3h Initialize System Management Manager
F4h Output one beep
F5h Boot to Mini DOS
F6h Clear Huge Segment
F7h Boot to Full DOS
* If the BIOS detects error 2C, 2E, or 30 (base 512K RAM error), it displays an additional word-bitmap
(xxxx) indicating the address line or bits that failed. For example, "2C 0002" means address line 1 (bit
one set) has failed. "2E 1020" means data bits 12 and 5 (bits 12 and 5 set) have failed in the lower 16
bits. Note that error 30 cannot occur on 386SX systems because they have a 16 rather than 32-bit bus.
The BIOS also sends the bitmap to the port-80 LED display. It first displays the check point code, followed
by a delay, the high-order byte, another delay, and then the low-order byte of the error. It repeats this se-
quence continuously.
16.6 PhoenixBIOS 4.0 Services
The ROM BIOS contains a number of useful run-time BIOS Services that are easily called by an out-
side program. As a programmer, you can execute these services, which are nothing more than sub-
routines, by invoking one of the BIOS interrupt routines (or, when specified, calling a protected-mode
entry point and offset). Invoking a software interrupt causes the CPU to fetch an address from the in-
terrupt table in low memory and execute the service routine. Some services return exit values in cer-
tain registers. All registers are preserved unless they return data or status.
Generally, a Carry flag set on exit indicates a failed service. A zero on exit in the AH register usually
indicates no error; any other value is the service's exit status code.
16.6.1 BIOS32 Service Directory
While the standard BIOS services are accessed through the interrupt table, newer services are ac-
cessed by a FAR CALL to a service entry point. Programmers can determine the entry point by
searching for a particular signature (such as "$PnP") in the BIOS range and finding the entry point in
the header.
The BIOS32 Service Directory (standard in PhoenixBIOS 4.0) provides a single entry point for all
those services in the BIOS that are designed for BIOS clients running in a 32-bit code segment, such
as 32-bit operating systems and 32-bit device drivers. The BIOS32 Service Directory itself is a 32-bit
BIOS service that provides a single entry point for the other 32-bit services. For a full description of
this service, see the Standard BIOS 32-Bit Service Directory Proposal, Rev 0.4 published by
Phoenix and available on the Phoenix Web site at:
http://www.phoenix.com/products/specs.html