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BSG Rocket info

HTIF

The HTIF protocol is based on a header(64 bits) and payload(N*64 bits), where N (number of packets) is defined in the header. However, the physical layer breakdown packets in 16-bits, starting from the LSB.

HTIF header

Header format (work in progress), where size = N = number of payload packets.

[63:24] [23:16] [15:4] [3:0]
csr-addr seqno size cmd

HTIF commands

The fesvr protocol is based on polling and it is always initiate by the host. In other words, the host(master) always sends requests and rocket(slave) acknowledge them.

type cmd value
request read mem 0
request write mem 1
request read csr 2
request write csr 3
response ack 4
response nack 5

HTIF CSR address

CSR name address
CSR_MTOHOST 0x0000000780
CSR_MFROMHOST 0x0000000781
CSR_MRESET 0x0000000782

HTIF polling packet

seqno stands for sequential number and it just a counter.

[63:24] [23:16] [15:4] [3:0]
0x0000000780 seqno 0x001 0x3

If the payload (64-bits) is different than zero, then there is something to be done.

HTIF exit() response packet

Header packet

[63:24] [23:16] [15:4] [3:0]
0x0000000780 seqno 0x001 0x4

Payload packet 0x0000000000000001

After this, CSR_MFROMHOST is set to 0x1 and rocket-reset is asserted back again by setting CSR_MRESET to 0x1.