Intel iapx 432 manual FONcrIOOS

OiAPTER 4

FONcrIOOS

This chapter describes the common facility that supports the execution of all Interface Processor functions. The first section shows hCM windCM 4 is used to provide access to the facility. The next section explains how a function is requested by writing operands and an o~""Ode through the windCM. The last two sections describe how the IP executes a requested function and returns status infonmation upon campletion of the operation.

4-1. FUNCrIOO FACILITY INTERFACE

Management of the IP function facility centers on the function request area of the processor data segment (see figure 4-1).Both the I/O controller software and the Interface Processor itself update and use the infonmation recorded in this area via the control window. Briefly, the IP records the status of the function request facility in the function state field; the I/O controller may obtain

status information by reading this field. The IP controller requests execution of a function by writing operands and an identifiying opcode into the function request area, and the IP reads these fields to obtain the infonmation it needs to execute the function. Finally, the execution of same functions produces a value which the IP records in the return-value field, where the IP controller can inspect it. Upon completion of any function, the IP updates the status infonmation am interrupts its Attached Processor. If desired, successful function completion interrupts can be disabled, thereby allowing only interrupts for unsuccessful completion to reach the AP.

In logical mode, the control window (window 4) is permanently opened onto the processor data segment and its mapping cannot be changed by

an ALTERMAP function request. By reading and wr i ting the corresponding PS memory subrange locations, the IP controller obtains access to fields in the function request area located in 432 memory. Notice that this interface mechanism is similar to a conventional memory-mapped peripheral device controller; the function request area fields are read and written like command, data and status registers.

Figure 4-2 illustrates the effect of executing a function, ALTER MAP AND SELECl' DATA SEG1ENT, which in this case alters the map of window o and selects a different 432 data segment. Window 4, the control windCM, is the only one through which function requests may be issued. Windows 0 through 3 are available for data transfer between a PS processor and 432 memory.

4-1