Intel E5472 Data Sheet - Page 71

Signal Definitions 5 Signal Definitions 5.1 Signal Definitions Table 5-1. Signal Definitions (Sheet 1 of 8) Name A[37:3]# A20M# ADS# ADSTB[1:0]# Type Description Notes I/O A[37:3]# (Address) define a 238-byte physical memory address 3 space. In sub-phase 1 of the address phase, these signals transmit the address of a transaction. In sub-phase 2, these signals transmit transaction type information. These signals must connect the appropriate pins of all agents on the FSB. A[37:3]# are protected by parity signals AP[1:0]#. A[37:3]# are source synchronous signals and are latched into the receiving buffers by ADSTB[1:0]#. On the active-to-inactive transition of RESET#, the processors sample a subset of the A[37:3]# lands to determine their power-on configuration. See Section 7.1. I If A20M# (Address-20 Mask) is asserted, the processor masks 2 physical address bit 20 (A20#) before looking up a line in any internal cache and before driving a read/write transaction on the bus. Asserting A20M# emulates the 8086 processor's address wrap- around at the 1 MB boundary. Assertion of A20M# is only supported in real mode. A20M# is an asynchronous signal. However, to ensure recognition of this signal following an I/O write instruction, it must be valid along with the TRDY# assertion of the corresponding I/O write bus transaction. I/O ADS# (Address Strobe) is asserted to indicate the validity of the 3 transaction address on the A[37:3]# lands. All bus agents observe the ADS# activation to begin parity checking, protocol checking, address decode, internal snoop, or deferred reply ID match operations associated with the new transaction. This signal must be connected to the appropriate pins on all Quad-Core Intel® Xeon® Processor 5400 Series FSB agents. I/O Address strobes are used to latch A[37:3]# and REQ[4:0]# on their 3 rising and falling edge. Strobes are associated with signals as shown below. Signals REQ[4:0]#, A[16:3]#, A[37:36]# A[35:17]# Associated Strobes ADSTB0# ADSTB1# AP[1:0]# I/O AP[1:0]# (Address Parity) are driven by the request initiator along 3 with ADS#, A[37:3]#, and the transaction type on the REQ[4:0]# signals. A correct parity signal is high if an even number of covered signals are low and low if an odd number of covered signals are low. This allows parity to be high when all the covered signals are high. AP[1:0]# must be connected to the appropriate pins of all Quad-Core Intel® Xeon® Processor 5400 Series FSB agents. The following table defines the coverage model of these signals. Request Signals A[37:24]# A[23:3]# REQ[4:0]# Subphase 1 AP0# AP1# AP1# Subphase 2 AP1# AP0# AP0# 71