diff options
Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 8 |
1 files changed, 7 insertions, 1 deletions
@@ -299,7 +299,8 @@ that can run one memory transfer at a time: The core initiates a memory transfer by asserting `mem_valid`. The valid signal stays high until the peer asserts `mem_ready`. All core outputs -are stable over the `mem_valid` period. +are stable over the `mem_valid` period. If the memory transfer is an +instruction fetch, the core asserts `mem_instr`. #### Read Transfer @@ -318,6 +319,11 @@ In a write transfer `mem_wstrb` is not 0 and `mem_rdata` is unused. The memory write the data at `mem_wdata` to the address `mem_addr` and acknowledges the transfer by asserting `mem_ready`. +The 4 bits of `mem_wstrb` are write enables for the four bytes in the addressed +word. Only the 8 values `0000`, `1111`, `1100`, `0011`, `1000`, `0100`, `0010`, +and `0001` are possible, i.e. no write, write 32 bits, write upper 16 bits, +write lower 16, or write a single byte respectively. + There is no need for an external wait cycle. The memory can acknowledge the write immediately with `mem_ready` going high in the same cycle as `mem_valid`, or `mem_ready` being tied to constant 1. |