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ACP Functions and Encoding  



Ancillary control process (ACP) functions can be expressed using seven function codes and four function modifiers. The function codes are:

The function modifiers are:

In addition to the function codes and modifiers, ACPs take five device- or function-dependent arguments, as shown in ACP Device- or Function-Dependent Arguments. The first argument, P1, is the address of the file information block (FIB) descriptor. File Information Block (FIB) describes the FIB in detail.

The second argument, P2, is an optional argument used in directory operations. It specifies the address of the descriptor for the file name string to be entered in the directory.

Argument P3 is the address of a word to receive the resultant file name string length. The resultant string is not padded. The actual length is returned in P3. Argument P4 is the address of a descriptor for a buffer to receive the resultant file name string. Both of these arguments are optional.  

Figure 1  ACP Device- or Function-Dependent Arguments  
ACP Device- or Function-Dependent Argument

The fifth argument, P5, is an optional argument containing the address of the attribute control block. Read/Write Attributes describes the attribute control block in detail.

All areas of memory specified by the descriptors must be capable of being read or written to.

ACP Device/Function Argument Descriptor Format shows the format for the descriptors. The count field is the length in bytes of the item described.  

Figure 2  ACP Device/Function Argument Descriptor Format  
ACP Device/Function Argument Descriptor Format


 
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