Data Sheet

Ethernet Controller I210 — Programming Interface
364
b. Bits 30:0 of IOADDR should hold the actual address of the internal register or memory being
written to.
2. Data to be written is written into the IODATA register.
— The IODATA register is used as a window to the register or memory address specified by
IOADDR register. As a result, the data written to the IODATA register is written into the CSR
pointed to by bits 30:0 of the IOADDR register.
3. IOADDR.Configuration IO Access Enable is cleared, to avoid un-intentional CSR read operations
(that might cause a clear by read) by other applications scanning the configuration space.
Software reads data from an internal CSR via configuration space in the following manner:
1. CSR address is written to the IOADDR register where:
a. Bit 31 (IOADDR.Configuration IO Access Enable) of the IOADDR register should be set to 1b.
b. Bits 30:0 of IOADDR should hold the actual address of the internal register or memory being
read.
2. CSR value is read from the IODATA register.
a. The IODATA register is used as a window to the register or memory address specified by IOADDR
register. As a result the data read from the IODATA register is the data of the CSR pointed to by
bits 30:0 of the IOADDR register
3. IOADDR.Configuration IO Access Enable is cleared, to avoid un-intentional CSR read operations
(that might cause a clear by read) by other applications scanning the configuration space.
Notes:
— In the event that the CSR_conf_en bit in the PCIe Init Configuration 2 Flash word is
cleared, accesses to the IOADDR and IODATA registers via the configuration address
space are ignored and have no effect on the register and the CSRs referenced by the
IOADDR register. In this case, any read access to these registers returns a value of 0b.
— When Function is in D3 state Software should not attempt to access CSRs via the
IOADDR and IODATA configuration registers.
— To enable CSR access via configuration space, Software should set bit 31 to 1b
(IOADDR.Configuration IO Access Enable) of the IOADDR register. Software should clear
bit 31 of the IOADDR register after completing CSR access to avoid an unintentional
clear-by-read operation or by another application scanning the configuration address
space.
— Bit 31 of the IOADDR register (IOADDR.Configuration IO Access Enable) has no effect
when initiating access via I/O address space.
— Software should access CSRs via I/O address space or configuration address space but
should not use both mechanisms at the same time.
8.1.2 Register Conventions
All registers in the I210 are defined to be 32 bits and should be accessed as 32-bit double-words;
however, there are some exceptions to this rule:
— Register pairs where two 32-bit registers make up a larger logical size.
— Accesses to Flash memory (via Expansion ROM space, secondary BAR space, or the I/O space)
might be byte, word or double word accesses.
Reserved bit positions: Some registers contain certain bits that are marked as reserved. These bits
should never be set to a value of 1b by software. Reads from registers containing reserved bits might
return indeterminate values in the reserved bit-positions unless read values are explicitly stated. When
read, these reserved bits should be ignored by software.