LAN9313 datasheet(59/398 Pages) SMSC

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Three Port 10/100 Managed Ethernet Switch with MII

Datasheet

SMSC LAN9313/LAN9313i

Revision 1.2 (04-08-08)

DATASHEET

6.2.2

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

CSR_BUSY (bit 31) set, the CSR_ADDRESS field (bits 15:0) set to the desired register address, the

R_nW (bit 30) set, and the AUTO_INC and AUTO_DEC fields cleared. Valid data is available for

reading when the 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 field written with the desired register address,

and the R_nW bit set. The completion of a read cycle is indicated by the clearing of the 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_INC and 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.

Figure 6.1 Switch Fabric CSR Write Access Flow Diagram

Idle

Write Data

Write

Command

Read

Command

CSR_BUSY = 0

CSR Write

CSR_BUSY = 1

Idle

Write Data

Write

Command

Read

Command

CSR_BUSY = 0

CSR Write Auto

Increment /

Decrement

CSR_BUSY = 1

Idle

Write

Direct

Data

Range

Read

Command

CSR_BUSY = 0

CSR Write Direct

Address

CSR_BUSY = 1

LAN9313 Datasheet(PDF) 59 Page - SMSC Corporation

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