added aknowledge pulse to ihu-ttx communication

git-svn-id: https://svn.spreadspace.org/mur.sat@239 7de4ea59-55d0-425e-a1af-a3118ea81d4c

1 files changed, 9 insertions, 1 deletions

diff --git a/doc/protocols/ihu-ttx.txt b/doc/protocols/ihu-ttx.txt
index d4fdcec..c91c479 100644
--- a/doc/protocols/ihu-ttx.txt
+++ b/doc/protocols/ihu-ttx.txt
@@ -14,6 +14,10 @@ The data is transferred MSB first in groups of 8bits (1 Octet). SDA must be
 stable before the clock goes high. A Clock pulse must be at least 4µs long and 
 the data has to stay valid for at least 17µs. After each octet there must be a 
 break of 50µs.
+After the last octet, which will be a checksum generated by the slave, the master 
+has to generate a single bit aknowledge. A logic low on SDA during a SCL pulse
+instructs the slave to process the received frame whereas a logic high tells the 
+slave to discard all data and proceed with normal operation.
 
 
      | wake up |               1st octet                        | break  |  2nd octet
@@ -33,13 +37,16 @@ Frames
 Every frame starts with 4 bit command code and a 4 bit length field. After this follow
 LEN octets of data. When all the data has been transferred the master (IHU) switches
 SDA to input and clocks in on byte as acknowledge. The aknowledge is a one byte XOR
-checksum over all octets (including the CMD/LEN octet).
+checksum over all octets (including the CMD/LEN octet). 
 
 Field-length:    1           LEN           1
             +---------+----------------+--------+
 Name        | CMD/LEN |      DATA      |   CS   |
             +---------+----------------+--------+
 
+As stated earlier a frame has only to be processed when a positive aknowledge has been
+sent by the master.
+
 Commands
 --------
 
@@ -97,3 +104,4 @@ Commands
  This transmits a new format string for the standard beacon. The data is a variable
  length string containing ASCII characters each standing for a beacon element to send
  out.
+