From 3ccbf6877e124989d415be9a3c8eaa38b02bdb7c Mon Sep 17 00:00:00 2001 From: Clifford Wolf Date: Sun, 3 Apr 2016 17:14:07 +0200 Subject: [PATCH] Added mem_wstrb documentation --- README.md | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/README.md b/README.md index 5cbc763..5821b58 100644 --- a/README.md +++ b/README.md @@ -319,6 +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.