Circuits Ram gate

Ram gate

Memory is split into 32-byte segments, accessible with 1-byte granularity
One gate up to 1MiB (32768 segments), little endian

C I O
T N U
L   T

0 0 0 - idle
1 C 0 - start of command, C is the command
...
1 C 0
0 C 0 - submit
0 0 1 - ack (if 0 then mem fault, idle for 128 ticks for safety)

Commands (LSB...MSB):

0 aaaaa - read from address (segAddr+aaaaa)
          chunkSize bytes will be read, chunks can cross segment boundary
10 aaaaa (dddd dddd)^cs - write chunkSize bytes
                          chunks can cross segment boundary 
11 00 x^(memLen-1) - set segment (for read/write)

11 01 0 xxxx - set memory len (in segments, log2, up to 32767 (1 MiB))

11 01 1 - set chunk size
        00 - 1 byte
        01 - 2 bytes
        10 - 4 bytes
        11 - reserved

11 10 - get memory len
         -> llll -> l -mem len in log2 segments


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Example communication

C I O
T N U
L   T

0 0 0
0 0 0 - idle

1 1 0
1 1 0
1 0 0
1 1 0
1 1 0 - set chunk size 

1 1 0
0 0 0 - to 4 bytes, also submit

0 0 1 - ack from memory

Example streams

C starts when CTL goes up
O starts when CTL went down tick before (ack in example before)

Starting memory (2 segments)

00 aa 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 
C -> O

// safe setup
11 01 10 -> 1 - set 4 byte chunk
11 10 -> 1 0001 - get memory len (returns 2)

11 01 0 0010 -> 1 - expand memory to 4 segments

11 00 0000 -> 1 - set segment to 0
0 00001 - 1 10101010 00000000 00000000 00000000 - read 4 bytes from address 1 seg 0
11 00 0001 -> 1 - set segment to 1
0 00001 - 1 11111111 11111111 00000000 00000000 - read 4 bytes from address 1 seg 1

10 11110 00010001 00010001 00010001 00010010 -> 1 - write 4 bytes from address 30 seg 1


End memory:


00 aa 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 11 11

11 11 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00