Intel iapx 432 manual

iAPX 432 Interface Processor Architecture Reference Manual

Canpleting a block node write transfer which is shorter than the byte count is a two-step process. First, the AP must issue an ALTER MAP AND SELECl'DATA SEGmNI' function with the entry state operand to "force termination" on window o. This causes the IP to empty its FIFO to 432 menory. Then, the AP must issue an additional ALTER MAP AND SELECI'DATA SEG1EN.I' FUNcrICN with an entry state operand to set window 0 invalid (close the window). If the AP attempts to close a block mode winda-t without first -forcing termination, the IP will generate a fault, interrupt the AP, and preserve the block nOOe window. When the transfer length is the same as the byte count attribute, the IP autanatically takes care of the last block which will be short if the transfer size is not a multiple of eight.

BLOCK moE TERMINATICN

A block node transfer will terminate oormally when all bytes have been transferred, or it may terminate prematurely should a fault occur. In both cases, the IP updates the transfer status attribute and issues an interrupt request to notify the Attached Processor. Following termination, any address reference falling in the subrange of window 0 will cause the windCM to fault and enter the error state. In the error state, requests for data transfer will be will be acknowledged (negatively) by the IP, but 00 data will be

transferred. This prevents a DMA controller, for example, fran continuing to transfer data after a fault has been det;.ected. The faul ted wimow cannot be re-used until it is closed and re-opened.

The IP tracks the progress of a block transfer by means of an on-chip byte oounter. The IP sets this counter equal to the byte count attribute when the window is opened and decrements it with each byte transferred. When the on-chip counter underflows (is decremented fran zero) all bytes have been transferred and the operation is terminated normally.

The IP will terminate a block transfer prematurely if it detects a

fault during the transfer. In addition, the I/O controller may itself force termination before the transfer has been completed. This is done by executing an ALTER MAP AND SELECr DATA SEGMENT function with the transfer status attribute set to "termination forced." Finally, termination may be forced by the IP's receipt of of any the interprocessor conmunication messages "suspend and fully requalify processor", "close windows", or "close windows am enter physical node".

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