Intel iapx 432 manual Physical Reekrence Mjoe

•	n	'it'	CHAPTER 5
			PHYSICAL REEKRENCE MJOE

The preceding chapters of this manual have Dmplicitly described the Interface Processor's logical reference node, its mrmal nnde of operation. The IP also provides ptzsical reference mode. Physical

reference mode is distinguished rom logical reference mode by direct 24-bit base-plus-displacement addressing and a l~ited subset of functions. It may be characterized as a powerful and rud~entary tool to be utilized in exceptional circumstances such as system initialization (see appendix E) and post-nnrtem diagnostics. This chapter first describes reference mode switching-hCM physical mode is entered and exited. The second section covers addressing and functions in physical reference mode.

5-1. REFERENCE lvDDE SWITCHING

An Interface Processor can switch from physical reference mode to logical reference mode (and vice versa) only under carefully controlled circumstances.

An Interface Processor enters physical reference mode in response to assertion of its INIT line dur ing system initialization (see iAPX 43203 VLSI Interface Processor Data Sheet, Order No. 171874) or upon receiving an "enter physical reference mode" IPC when in logical node. Sioce a "send to processor" IPC requires an access descriptor with the proper right for the target processor's processor object, the ability of 432 software to place an IP in physical reference mode can be l~ited by restricting distributioo of this right in IP

processor object references. However, any 432 process with an access descr iptor for a processor obj ect . with "broadcast to processors" rights can place all IPs into physical mode by

broadcasting the "enter physical reference mode" IPC. Thus, processors should only be granted broadcast rights with careful precautions. Table E-l shows the attributes of the IP windows after entering physical reference mode.

An Interface Processor exits physical reference nnde and enters logical reference mode when it receives a local IPC (it ignores global IPCs in physical IlPde). This local IPC is considered a startup IPC. The response of IP is to qualify the processor, enter logical node, and then respond to the IPC.

5-1