LAN9303MI-AKZE Datasheet, PDF (69/386 Pages) SMSC Corporation – Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII

Small Form Factor Three Port 10/100 Managed Ethernet Switch with Dual MII/RMII/Turbo MII
Datasheet
CSR Write
Idle
CSR Write Auto
Increment /
Decrement
Idle
CSR Write Direct
Address
Idle
Write Data
Register
Write
Command
Register
Write
Direct
Data
Register
Range
Write
Command
Register
Write Data
Register
CSR_BUSY = 0
Read
Command
Register
CSR_BUSY = 1
6.2.2
CSR_BUSY = 0
Read
Command
Register
CSR_BUSY = 0
CSR_BUSY = 1
Read
Command
Register
CSR_BUSY = 1
Figure 6.1 Switch Fabric CSR Write Access Flow Diagram
Switch Fabric CSR Reads
To perform a read of an individual Switch Fabric register, the read cycle must be initiated by performing
a single write to the Switch Fabric CSR Interface Command Register (SWITCH_CSR_CMD) with the
CSR Busy (CSR_BUSY) bit set, the CSR Address (CSR_ADDR[15:0]) field set to the desired register
address, the Read/Write (R_nW) bit set, and the Auto Increment (AUTO_INC) and Auto Decrement
(AUTO_DEC) fields cleared. Valid data is available for reading when the CSR Busy (CSR_BUSY) bit
is cleared, indicating that the data can be read from the Switch Fabric CSR Interface Data Register
(SWITCH_CSR_DATA).
A second read method may be used which utilizes the auto increment/decrement function of the Switch
Fabric CSR Interface Command Register (SWITCH_CSR_CMD) for reading sequential register
addresses. When using this method, the Switch Fabric CSR Interface Command Register
(SWITCH_CSR_CMD) must first be written with the Auto Increment (AUTO_INC) or Auto Decrement
(AUTO_DEC) bit set, the CSR Address (CSR_ADDR[15:0]) field written with the desired register
address, and the Read/Write (R_nW) bit set. The completion of a read cycle is indicated by the clearing
of the CSR Busy (CSR_BUSY) bit, at which time the data can be read from the Switch Fabric CSR
Interface Data Register (SWITCH_CSR_DATA). When the data is read, the address in the Switch
Fabric CSR Interface Command Register (SWITCH_CSR_CMD) is incremented or decremented
accordingly, and another read cycle is started automatically. The user should clear the Auto Increment
(AUTO_INC) and Auto Decrement (AUTO_DEC) bits before reading the last data to avoid an
unintended read cycle.
Figure 6.2 illustrates the process required to perform a Switch Fabric CSR read.
SMSC LAN9303M/LAN9303Mi
69
DATASHEET
Revision 1.5 (07-08-11)