SMSC LAN9311 Manual De Usuario

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface

Revision 1.4 (08-19-08)

56

SMSC LAN9311/LAN9311i

 

To perform a write to an individual switch fabric register, the desired data must first be written into the

. The write cycle is initiated by

p e r f o r m i n g   a   s i n g l e   w r i t e   t o   t h e  

 with CSR_BUSY (bit 31) set, the CSR_ADDRESS field (bits 15:0) set to the

desired register address, the R_nW (bit 30) cleared, the AUTO_INC and AUTO_DEC fields cleared,
and the desired CSR byte enable bits selected (bits 19:16). The completion of the write cycle is
indicated by the clearing of the CSR_BUSY bit.

A second write method may be used which utilizes the auto increment/decrement function of the

 for writing sequential register

addresses. When using this method, the 

 must first be written with the auto increment(AUTO_INC) or auto

decrement(AUTO_DEC) bit set, the CSR_ADDRESS field written with the desired register address, the
R_nW bit cleared, and the desired CSR byte enable bits selected (typically all set). The write cycles
are then initiated by writing the desired data into the 

. The completion of the write cycle is indicated by the clearing of the

CSR_BUSY bit, at which time the address in the 

 is incremented or decremented accordingly. The user may then initiate a

subsequent write cycle by writing the desired data into the 

.

The third write method is to use the direct data range write function. Writes within the 

 address range automatically set

the appropriate register address, set all four byte enable bits (CSR_BE[3:0]), clears the R_nW bit, and
s e t s   t h e   C S R _ B U S Y   b i t   o f   t h e  

. The completion of the write cycle is indicated by the clearing of the

CSR_BUSY bit. Since the address range of the switch fabric CSRs exceeds that of the 

 address range, a sub-set of the

switch fabric CSRs are mapped to the 

 address range as detailed in 

 illustrates the process required to perform a switch fabric CSR write. The minimum wait

periods as specified in 

 are required where

noted.