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KSZ8873MLLJ Datasheet(PDF) 38 Page - Micrel Semiconductor
MICREL [Micrel Semiconductor]
KSZ8873MLLJ Datasheet(HTML) 38 Page - Micrel Semiconductor
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SPI Slave Serial Bus Configuration
In managed mode, the KSZ8873MLLJ can be configured as a SPI slave device. In this mode, a SPI master device
(external controller/CPU) has complete programming access to the KSZ8873MLLJ’s 198 registers. Programming access
includes the Global Registers, Port Registers, Advanced Control Registers and indirect access to the “Static MAC Table”,
“VLAN Table”, “Dynamic MAC Table” and “MIB Counters”. The tables and counters are indirectly accessed via registers
121 to 131.
The KSZ8873MLLJ supports two standard SPI commands: ‘0000_0011’ for data read and ‘0000_0010’ for data write. SPI
multiple read and multiple write are also supported by the KSZ8873MLLJ to expedite register read back and register
SPI multiple read is initiated when the master device continues to drive the KSZ8873MLLJ SPISN input pin (SPI Slave
Select signal) low after a byte (a register) is read. The KSZ8873MLLJ internal address counter increments automatically
to the next byte (next register) after the read. The next byte at the next register address is shifted out onto the
KSZ8873MLLJ SPIQ output pin. SPI multiple read continues until the SPI master device terminates it by de-asserting the
SPISN signal to the KSZ8873MLLJ.
Similarly, SPI multiple write is initiated when the master device continues to drive the KSZ8873MLLJ SPISN input pin low
after a byte (a register) is written. The KSZ8873MLLJ internal address counter increments automatically to the next byte
(next register) after the write. The next byte that is sent from the master device to the KSZ8873MLLJ SDA input pin is
written to the next register address. SPI multiple write continues until the SPI master device terminates it by de-asserting
the SPISN signal to the KSZ8873MLLJ.
For both SPI multiple read and multiple write, the KSZ8873MLLJ internal address counter wraps back to register address
zero once the highest register address is reached. This feature allows all 198 KSZ8873MLLJ registers to be read, or
written with a single SPI command from any initial register address.
The KSZ8873MLLJ is capable of supporting a SPI bus.
The following is a sample procedure for programming the KSZ8873MLLJ using the SPI bus:
1. At the board level, connect the KSZ8873MLLJ pins as follows:
KSZ8873MLLJ Pin #
KSZ8873MLLJ Signal Name
External Processor Signal Description
SPI Slave Select
(Master output; Slave input)
(Master input; Slave output)
Table 9. SPI Connections
2. Enable SPI slave mode by setting the KSZ8873MLLJ strap-in pins P2LED[1:0] to “10”.
3. Power up the board and assert reset to the KSZ8873MLLJ.
4. Configure the desired register settings in the KSZ8873MLLJ, using the SPI write or multiple write command.
5. Read back and verify the register settings in the KSZ8873MLLJ, using the SPI read or multiple read command.
Some of the configuration settings, such as “Aging enable”, “Auto Negotiation Enable”, “Force Speed” and “Power down” can
be programmed after the switch has been started.
The following four figures illustrate the SPI data cycles for “Write”, “Read”, “Multiple Write” and “Multiple Read”. The read data is
registered out of SPIQ on the falling edge of SPIC, and the data input on SPID is registered on the rising edge of SPIC.
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