HP Vectra Technical Reference Manual page 441

EX-BIOS drivers do not usually enable interrupts (STI) while processing this function code. Drivers
should service this interrupt within 250 microseconds or maintain interrupts off for no more than
250 microseconds at a time. Drivers should expect 40 bytes of stack when called. If a driver
enables interrupts it must provide 40 bytes of stack for other ISR's.
On Entry: AH
=
F _ISR
On Exit: AH
=
RS_SUCCESSFUL
or RS_NOT_SERVICED
F_SYSTEM (AH
=
02H)
This function contains a set of subfunctions that execute system-oriented tasks. These
subfunctions include driver setup, configuration, and control. The F_SYSTEM subfunctions are
described in detail below.
SF _INIT (AX = 0200H)
This starts the initialization process of a driver. The function does not return to the caller until the
driver is ready to be called by another driver. All system services (V_SYSTEM) are assumed to be
operational when a driver is called by this function.
~
The driver is responsible for a brief hardware check and to report RS_FAIL if the test failed. A
driver need only execute a test procedure if it directly interfaces to physical hardware.
If the driver requires EX-BIOS RAM the BX and DX registers can be used to reserve available
memory (see Section 9).
On Entry: AH
=
F_SYSTEM (02H)
AL
=
SF_INIT
(OOH)
BX
=
"Iast used
DS"
BP
=
Driver's vector address
On Exit: AH
=
Return Status Code
BX
=
New "Iast used DS"
Recommended for hardware test failure:
AH
=
RS_FAIL
ES:DI
=
pointer to a string of information about the nature of the error
CX
=
length of the string pointed to by ES:DI
432 Driver Writer's Guide