Lenovo PC 300PL Technical Information Manual 6275, 6285 - Page 63

Hard Disk Drives and Controller, Software Compatibility, Software Interrupts

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Chapter 7. System Compatibility Hard Disk Drives and Controller Reading from and writing to the hard disk is initiated in the same way as in IBM Personal Computer products; however, new functions are supported. Software Compatibility To maintain software compatibility, the interrupt polling mechanism that is used by IBM Personal Computer products is retained. Software that interfaces with the reset port for the IBM Personal Computer positive-edge interrupt sharing (hex address 02Fx or 06Fx, where x is the interrupt level) does not create interference. Software Interrupts With the advent of software interrupt sharing, software interrupt routines must daisy chain interrupts. Each routine must check the function value, and if it is not in the range of function calls for that routine, it must transfer control to the next routine in the chain. Because software interrupts are initially pointed to address 0:0 before daisy chaining, check for this case. If the next routine is pointed to address 0:0 and the function call is out of range, the appropriate action is to set the carry flag and do a RET 2 to indicate an error condition. Machine-Sensitive Programs Programs can select machine-specific features, but they must first identify the machine and model type. IBM has defined methods for uniquely determining the specific machine type. The machine model byte can be found through Interrupt 15H, Return System Configuration Parameters function (AH)=C0H). Chapter 7. System Compatibility 51

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Chapter 7.
System Compatibility
Hard Disk Drives and Controller
Reading from and writing to the hard disk is initiated in the same way as in IBM Personal Computer
products; however, new functions are supported.
Software Compatibility
To maintain software compatibility, the interrupt polling mechanism that is used by IBM Personal Computer
products is retained.
Software that interfaces with the reset port for the IBM Personal Computer
positive-edge interrupt sharing (hex address 02F
x
or 06F
x
, where
x
is the interrupt level) does not create
interference.
Software Interrupts
With the advent of software interrupt sharing, software interrupt routines must daisy chain interrupts.
Each
routine must check the function value, and if it is not in the range of function calls for that routine, it must
transfer control to the next routine in the chain.
Because software interrupts are initially pointed to
address 0:0 before daisy chaining, check for this case.
If the next routine is pointed to address 0:0 and
the function call is out of range, the appropriate action is to set the carry flag and do a RET 2 to indicate
an error condition.
Machine-Sensitive Programs
Programs can select machine-specific features, but they must first identify the machine and model type.
IBM has defined methods for uniquely determining the specific machine type.
The machine model byte
can be found through Interrupt 15H, Return System Configuration Parameters function (AH)=C0H).
Chapter 7.
System Compatibility
51