|Name|Type  |Length|Address|Write or Read Value|
|Bits|19..18|17..16|15..0  |31..0              |

Type:
00: Read from CSR
01: Write to CSR
10: Read SPI Controller regs
11: Write SPI Controller regs

Length of Value:
00: Byte
01: Halfword
10: Word
11: Reserved

Address:
16-bit address to access CSR or SPI controller register

Write or Read Value:
32-bit value (always 32-bits, the Length controls which bytes we care about)

Written value from RP2040 => Stellar
Read value from Stellar => RP2040
Minimum number of clock cycles before Write takes effect/Read data is ready to be read TBD