lan9311 Standard Microsystems Corp., lan9311 Datasheet - Page 57

• Manufacturer Part Number: lan9311
• Description: Lan9311/lan9311i Two Port 10/100 Managed Ethernet Switch With 16-bit Non-pci Cpu Interface
• Manufacturer: Standard Microsystems Corp.

Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9311/LAN9311i
6.2.2
CSR_BUSY = 0
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
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
CSR Interface Data Register
A second read method may be used which utilizes the auto increment/decrement function of the
Fabric CSR Interface Command Register (SWITCH_CSR_CMD)
addresses. When using this method, the
(SWITCH_CSR_CMD)
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_CSR_DATA). When the data is read, the address in the
Command Register (SWITCH_CSR_CMD)
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
periods as specified in
noted.
CSR Write
Write Data
Command
Command
Register
Register
Register
illustrates the process required to perform a switch fabric CSR read. The minimum wait
Write
Read
Idle
Figure 6.1 Switch Fabric CSR Write Access Flow Diagram
min wait period
CSR_BUSY = 1
Switch Fabric CSR Interface Command Register (SWITCH_CSR_CMD)
Table 8.1, “Read After Write Timing Rules,” on page 103
must first be written with the auto increment(AUTO_INC) or auto
CSR_BUSY = 0
(SWITCH_CSR_DATA).
CSR Write Auto
DATASHEET
Increment /
Decrement
Command
Write Data
Command
Register
Register
Register
Write
Read
Idle
57
is incremented or decremented accordingly, and another
min wait period
Switch Fabric CSR Interface Command Register
CSR_BUSY = 1
Switch Fabric CSR Interface Data Register
CSR_BUSY = 0
CSR Write Direct
Address
for reading sequential register
Command
Register
Register
Range
Direct
Switch Fabric CSR Interface
Write
Read
Data
Idle
min wait period
CSR_BUSY = 1
Revision 1.2 (04-08-08)
are required where
Switch Fabric
Switch
with