Document terminal write feature

where start addres isn't needed

src/avrdude.1

@@ -910,6 +910,11 @@ needs eight bytes as it is the same as 0xFFFFffffFFFFffffU.
 One trailing comma at the end of
 .Ar data
 items is ignored to facilitate copy & paste of lists.
+.It Ar write memory data
+The start address
+.Ar addr
+may be omitted if the size of the memory being written to is
+1 byte in size.
 .It Ar write memory addr len data[,] {data[,]} ...
 The ellipsis ... form writes <len> bytes padded by repeating the last
 .Ar data

src/doc/avrdude.texi

@@ -1616,6 +1616,10 @@ eight bytes as it is the same as @code{0xFFFFffffFFFFffffU}.
 One trailing comma at the end of data items is ignored to facilitate copy
 and paste of lists.
 
+@item write @var{memtype} @var{addr} @var{data}
+The start address @code{addr} may be omitted if the size of the memory
+being written to is 1 byte in size.
+
 @item write @var{memtype} @var{addr} @var{length} @var{data[,]} @{@var{data[,]}@} @dots{}
 The ellipses form @dots{} of write is similar to above, but @var{length}
 byte of the memory are written. For that purpose, after writing the