IDT 89HPES12T3G2, Preliminary User'S Manual

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IDT
PES12T3G2 User Manual 3 January 28, 2013
Notes
Figure 2 Example of Byte Ordering for “Big Endian” or “Little Endian” System Definition
Register Terminology
Software in the context of this register terminology refers to modifications made by PCIe root configura-
tion writes to registers made through the slave SMBus interface or serial EEPROM register initialization.
See Table 2.
Type Abbreviation Description
Hardware Initialized HWINIT Register bits are initialized by firmware or hardware mechanisms
such as pin strapping or serial EEPROM. (System firmware hard-
ware initialization is only allowed for system integrated devices.)
Bits are read-only after initialization and can only be reset (for
write-once by firmware) with reset.
Read Only and Clear RC Software can read the register/bits with this attribute. Reading the
value will automatically cause the register/bit to be reset to zero.
Writing to a RC location has no effect.
Read Clear and Write RCW Software can read the register/bits with this attribute. Reading the
value will automatically cause the register/bits to be reset to zero.
Writes cause the register/bits to be modified.
Reserved Reserved The value read from a reserved register/bit is undefined. Thus,
software must deal correctly with fields that are reserved. On
reads, software must use appropriate masks to extract the defined
bits and not rely on reserved bits being any particular value. On
writes, software must ensure that the values of reserved bit posi-
tions are preserved. That is, the values of reserved bit positions
must first be read, merged with the new values for other bit posi-
tions and then written back.
Read Only RO Software can only read registers/bits with this attribute. Contents
are hardwired to a constant value or are status bits that may be
set and cleared by hardware. Writing to a RO location has no
effect.
Read and Write RW Software can both read and write bits with this attribute.
Table 2 Register Terminology (Part 1 of 2)
0 1 2 3
bit 0 bit 31
Address of Bytes within Words: Big Endian
3 2 1 0
bit 0 bit 31
Address of Bytes within Words: Little Endian