System Services

 

Function Number	Function
0x90	Allocate port
0x91	Allocate list of ports
0x94	Read from IO port
0x95	Read string from IO port
0x98	De-allocate port
0x99	De-allocate list of ports
0x9C	Write to IO port
0x9D	Write string to IO port
0xA0	Allocate IRQ
0xA1	Allocate priority IRQ
0xA4	End of IRQ
0xA7	Allocate CPU interrupt
0xA8	De-allocate IRQ
0xAF	De-allocate CPU interrupt
0xEF	Hook CPU interrupts
0xF0	Self Test
0xF1	Idle
0xFE	Shutdown module

 

This service allocates a single IO port.

Input
  BX    Port number
  CX    Code ID of owner

Output
  AL    status
 

0x91    Allocate list of ports

This service allocates multiple IO ports, taken from a 0 terminated list of word sized port numbers. If an error is encountered no ports will be allocated.

Input
  EBX    Address of list
  CX     Code ID of owner

Output
  AL    status

 
0x94    Read from IO port

This reads an IO port.

Input
  BL     Read size
          0 = byte
          1 = word
          2 = dword
  CX     Code ID of owner
  DX     IO Port number

Output
  EBX    Returned value
  AL     status
 

0x95    Read string from IO port

This reads an IO port multiple times. Data read is stored in a buffer.

Input
  BL     Read size
          0 = byte
          1 = word
          2 = dword
  CX     Code ID of owner
  DX     IO Port number
  ESI    Number of reads
  EDI    Address of buffer

Output
  EBX    Number of bytes read
  AL     status
 

0x98    De-allocate port

This service allocates a single IO port.

Input
  BX    Port number
  CX    Code ID of owner

Output
  AL    status
 

0x99    De-allocate list of ports

This service allocates multiple IO ports, taken from a 0 terminated list of word sized port numbers. If an error occurs as many ports will be de-allocated as possible.

Input
  EBX    Address of list
  CX     Code ID of owner

Output
  AL    status
 

0x9C    Write to IO port

This writes to an IO port.

Input
  BL     Write size
          0 = byte
          1 = word
          2 = dword
  CX     Code ID of owner
  DX     IO Port number
  ESI    Value to write

Output
  AL     status
 

0x9D    Write string to IO port 

This sends a buffer out to an IO port.

Input
  BL     Write size
          0 = byte
          1 = word
          2 = dword
  CX     Code ID of owner
  DX     IO Port number
  ESI    Number of writes
  EDI    Address of buffer

Output
  EBX    Number of bytes written
  AL     status
 
 

0xA0    Allocate IRQ

This service allocates and enables an IRQ (using the PIC) and creates a trap gate for it. Trap gates don't automatically disable interrupts.

Input
  BL     IRQ number
  CX     Code ID of owner
  EDX    Offset of interrupt handler

Output
  AL    status
 

0xA1    Allocate priority IRQ

This service allocates and enables an IRQ (using the PIC) and creates an interrupt gate for it. Interrupt gates automatically disable interrupts.

Input
  BL     IRQ number
  CX     Code ID of owner
  EDX    Offset of interrupt handler

Output
  AL    status
 

0xA4    Signal end of IRQ

This service should only be called IRQ interrupt handlers before ending the interrupt (with IRETD).

Input
  BL     IRQ number

Output
  AL    status
 

0xA7    Allocate CPU interrupt 

The service can be used by system modules and drivers only. When one or more CPU interrupts are allocated to some code that code will be called by system services when/if that interrupt occurs. See debugging for details.

Input
  BL     Interrupt number
  CX     Code ID of owner
  EDX    Offset of handler

Output
  AL    status
 

0xA8    De-allocate IRQ

This service de-allocates and disables an IRQ (using the PIC) and deletes the interrupt descriptor for it.

Input
  BL     IRQ number
  CX     Code ID of owner

Output
  AL    status
 

0xAF    De-allocate CPU interrupt

This service de-allocates interrupts allocated with system service 0xA7.

Input
  BL     Interrupt number
  CX     Code ID of owner

Output
  AL    status
 

0xEF    Hook CPU interrupts

This should only ever be called by time services during boot. See debugging for details.

Input
  none

Output
  AL     status
 
 

0xF0    Self Test

This service test the system services data structures.

Input
  none

Output
  EBX    address of error string (unless no error)
  AL     status
 

0xF1    Idle

This is used to give the system services idle time. It's normally only ever used by time services.

Input
  none

Output
  AL     status (0 means ok, no error string)
 
 
0xFE    Shutdown module 

This de-allocates all resources used. Interrupts must be disabled before removing the system services, and they should not be enabled again until another system services has taken it's place. The code selector returned by this service should be de-allocated by the caller.

Input
  none

Output
  bx    Code Selector