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Update proto.md #2

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Update proto.md #2

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0ccfc93
fix formatting in proto.md
mdavidsaver Apr 2, 2024
3ffa583
proto.md change header formatting
mdavidsaver Apr 2, 2024
23f7e35
document alt. ROM location
mdavidsaver Apr 2, 2024
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38 changes: 20 additions & 18 deletions proto.md
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Original file line number Diff line number Diff line change
@@ -1,14 +1,12 @@
LBNL Embedded Ethernet Protocol
===============================
# LBNL Embedded Ethernet Protocol

A Request/Reply style protocol using UDP on port 50006.
A Device (Server) receives Requests on port 50006 and responds to each valid Request with a single Reply.

Requests and Replies act on 32-bit registers in a 64MB address space.
The 24-bit Address field acts as the upper bits of a 26-bit address.

UDP Message Format
------------------
## UDP Message Format

<pre>
0 1 2 3
Expand Down Expand Up @@ -44,8 +42,7 @@ Message fields are in Most Significant Byte first (MSB or network) byte order.

It is _suggested_ to pad messages shorter than 32 bytes with reads of address 0.

Message Fields
--------------
## Message Fields

### Header

Expand Down Expand Up @@ -76,8 +73,7 @@ When Bits[4] is clear (Write operation) this field contains the value to be writ

To read back the actual value of a register after a write operation, a Read operation with the same address may be added following a Write within the same message.

Example message
---------------
## Example message

Request

Expand Down Expand Up @@ -109,8 +105,7 @@ A corresponding Reply might be:
* A write of address 0x10000 with 0x12345678 is echoed.
* Address 0x10000 reads 0x00345678 (perhaps due to truncation)

Required Registers
------------------
## Required Registers

### 0x000000 - 0x000003

Expand All @@ -125,8 +120,16 @@ The first 4 registers will read back the 16 byte constant value "Hello World!\r\
These 2048 registers access static configuration data.
See section Configuration ROM.

Configuration ROM Format
------------------------
If 0x800 has a zero (0) value, then the altnerate ROM location
should be used.

### Alternate ROM location

Consists of 16384 registers 0x004000 - 0x007fff
containing static configuration data.
See section Configuration ROM.

## Configuration ROM Format

The register range 0x800 - 0xfff holds static data describing the device.
In each 4 byte register, only the 2 lower bytes are used.
Expand Down Expand Up @@ -186,8 +189,7 @@ Contains:
* Type 1 Descriptor with length 3 holding the string "Hello\0".
* Type 0 Descriptor indicating end of ROM

JSON Information
----------------
## JSON Information

The JSON blob encoded in the Configuration ROM will contain a Object (aka. mapping or dictionary).
The keys of this dictionary are symbolic register names,
Expand All @@ -209,9 +211,9 @@ The (first) Address of this register.
Determines number of Addresses which constitute this register.
Number of Addresses is 2 to the power of addr_width.

<pre>
```
naddrs = 1u<<addr_width;
</pre>
```

eg. an addr_width of 0 defines a register with exactly one Address.

Expand All @@ -229,7 +231,7 @@ An arbitrary string describing this register.

### Example

<pre>
```
{
"J18_debug": {
"access": "r",
Expand All @@ -242,4 +244,4 @@ An arbitrary string describing this register.
"special": "sauce"
}
}
</pre>
```
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