KSZ8462HL Datasheet, PDF (84/279 Pages) Micrel Semiconductor – IEEE 1588 Precision Time Protocol-Enabled Two-Port 10/100Mb/s Ethernet Switch with 8 or 16 Bit Host Interface

Micrel, Inc.
KSZ8462HL/KSZ8462FHL
two write accesses) into KSZ8462 when CMD (Command type) pin is high. The BIU qualifies the CSN pin as well as the
read enable (RDN) or write enable (WRN) pin to read or write the SD[15:0] (16−bit mode) or SD[7:0] (8−bit mode) data
value from or to KSZ8462 when command type (CMD) pin is low.
In order for software to read back the previous CMD register write value when CMD is “1”, the BIU qualifies both the CSN
pin and the RDN pin to read the Address A[10:2] and BE[3:0] value (in 16−bit mode) back from the KSZ8462 when CMD
pin is high. Reading back the addresses in 8−bit mode is not a valid operation.
BIU Summary
Figure 20 shows the connection for different data bus sizes.
All of control and status registers in the KSZ8462 are accessed indirectly depending on CMD pin. The command
sequence to access the specified control or status register is to write the register’s address (when CMD = “1”) then read or
write this register data (when CMD = “0”). If both RDN and WRN signals in the system are only used for KSZ8462, the
CSN pin can be forced to active low to simplify the system design. The CMD pin can be connected to host address line
HA[0] for 8−bit bus mode or HA[1] for 16−bit bus mode.
Figure 20. KSZ8462 8-Bit and 16-Bit Data Bus Connections
Example:
Assume that the register space is located at an external I/O base address of 0x0300, a 16-bit data path is used, and it is
desired to read two bytes of data from address 0xD0:
• External address decoding should decode the 0x0300 base address and create a signal for the CSN pin.
• The host address line 1 (HA[1]) is connected to the CMD input pin. For a host write to the device, the HA[1] being
asserted will make CMD = “1” which will indicate that the data on the DS[15:0] bus are address and byte enable bits.
• As shown in Figure 23, the address bits A[10:2] are on SD[10:2].
• Write a value of 0x30D0 (register offset of 0xD0 with BE[1:0] (set on the SD[16:0] bus) to address 0x0302. (This sets up
the address for the upcoming read operation by writing the desired destination address to be read.)
• Read the value from address 0x0300 with HA[1] = 0 (CMD =” “0”). The CSN pin is driven again by the decode of the
base address of 0x0300.
June 11, 2014
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Revision 1.0