TS-4800 SPI

From Technologic Systems Manuals

This core is for high speed SPI with auto-CS#. Starts at offset 0x40 on the this series. Chip select #0 is typically used for onboard spiflash. Chip select #1 is used for offboard spiflash. The last 2 chip selects are always available on the Cavium series boards.

The SPI controller is an FPGA core which is accessed using spictl. The simplest method for communication is calling spictl through bash:

# Read 32 bytes from LUN1
spictl --lun=1 --readstream=32

# Write Hello (68:65:6c:6c:6f)
spictl --lun=1 --writestream=68:65:6c:6c:6f


ts4800:~# spictl --help
Technologic Systems SPI controller manipulation.

General options:
-c | --clock=frequency    SPI clock frequency
-e | --edge=value         set clock edge (positive for > 0, negative for < 0)
-w | --writestream=data   write colon delimited hex octets to SPI
-d | --readwrite=data     write colon delimited hex octets to SPI while reading to stdout
-r | --readstream=bytes   read specified number of bytes from SPI to stdout
-o | --holdcs             don't de-assert CS# when done
-l | --lun=id             Talk to specified chip number
-s | --server=<port>      Daemonize and run as server listening on port
-p | --port=<host><:port> Talk to spictl server
hex octets are hexadecimal bytes. for example,
this command reads 32 bytes of CS#1 SPI flash from address 8192:
./spictl -l 1 -w 0B:00:20:00:00 -r 32

The spictl utility can also run as a TCP server which lets you easily access SPI in your application. To start the tcp server on port 7755:

spictl --server=7755

The data stream packet to a spictl server consists of opcodes and operands. Each opcode is one byte long and may encode part or all of the operand. Some opcodes specify that additional bytes of data follow to contain the remainder of the operands.

There are four opcodes encoded in the two msb of the opcode byte:

    • The chip number is encoded in the two LSB.
      • 00 = CS#0
      • 01 = CS#1
      • 10 = CS#2
      • 11 = CS#3
    • If Bit 5 is set, OPCODE = ASSERT CHIP SELECT.
    • Then If Bit 3 is set, Bit 2 is the new SPI edge to use (1 = positive edge, 0 = negative edge). Also, two additional bytes follow as operands. These two bytes are a big-endian encoded clock value. This value multiplied by 2048 is the SPI clock frequency to use. If Bit 5 is clear, OPCODE = DE-ASSERT CHIP SELECT
    • The number of bytes to read must be a power of two, encoded in the 6 lsb. These six bits represent the number to raise 2 to the power of to get the length. So,
      • 00_0000 = 1 byte
      • 00_0001 = 2 bytes
      • ...
      • 00_1100 = 4096 bytes
    • The number of bytes to write is encoded in the same manner as for a READ opcode. After the opcode byte, the number of bytes to write follows as the operands.
    • This opcode encodes identically as the WRITE opcode. However it specifies that bytes are to be READ as well as written.

You can also use the spictl --server=<port> and run a second invokation of spictl with --port=<port> to have the second instance act as a client to the server. You can then use tcpdump to see the exact tcp packets being sent back and forth for various operations.

The table below is the register map for the SPI in the FPGA:

Offset Access Bit(s) Description
0x40 Read Only 15 SPI MISO state
Read/Write 14 SPI CLK state
Read/Write 13:10 Speed - 0 (highest), 1 (1/2 speed), 2 (1/4 speed)...
Read/Write 9:8 LUN (0-3 representing the 4 chip selects)
Read/Write 7 CS (1 - CS# is asserted)
N/A 6:1 Reserved
Read/Write 0 Speed
0x42 Read Only 16:0 Previous SPI read data from last write
0x44 N/A 16:0 Reserved
0x46 N/A 16:0 Reserved
0x48 Read/Write 16:0 SPI read/write with CS# to stay asserted
0x4a Read Only 16:0 SPI pipelined read with CS# to stay asserted
0x4c Read/Write 16:0 SPI Read/Write with CS# to deassert post-op
0x4e N/A 16:0 Reserved

The SPI clk state register should be set when CS# is deasserted. Value 0 makes SPI rising edge (CPOL=0), 1 is falling edge (CPOL=1). This only applies to speed >= 1. For speed == 0, SPI clock polarity/skew must be set from the PLL phase adjust registers in the syscon block.

Where the base clock is 75Mhz (extended temp alters this to 50Mhz), speed settings break down as follows:

 0 - 75Mhz (/1)
 1 - 37.5Mhz (/2)
 2 - 18.75Mhz (/4)
 3 - 12.5Mhz (/6)
 4 - 9.375Mhz (/8)
 5 - 7.5Mhz (/10)
 6 - 6.25Mhz (/12)
 7 - 5.36Mhz (/14)
 8 - 4.68Mhz (/16)
 9 - 4.17Mhz (/18)
 15 - 2.5Mhz (/30)
 19 - 1.97MHz (/38)
 31 - 1.21MHz (/62)

The pipelined read register is for read bursts and will automatically start a subsequent SPI read upon completion of the requested SPI read. Reading from this register infers that another read will shortly follow and allows this SPI controller "a head start" on the next read for optimum read performance. This register should be accessed as long as there will be at least one more SPI read with CS# asserted to take place. This register is an appropriate target address for SBUS burst reads.