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--- megacode [2014/12/28 19:08] – mdru kingkevin
+++ megacode [2014/12/28 19:47] – [protocol] kingkevin
@@ Line 46: / Line 46: @@
 In [[https://www.cuvoodoo.info/?post_type=podcast&p=41|episode #005]] I presented how the receiving part works, so to record codes and analyze them.
-====== MDR ======
+==== MDR ====
 The main target is the [[http://www.linearcorp.com/product_detail.php?productId=941|MDR]] from the [[http://www.linearcorp.com/|Linear]] [[http://www.linearcorp.com/radio_control.php#megacode|MegaCode series]].
@@ Line 67: / Line 67: @@
 This chip can also come as One Time Programmable, and might be factory programmed.
-====== MDR-U ======
+==== MDR-U ====
 The main target is the [[http://www.linearcorp.com/product_detail.php?productId=942|MDR-U]] from the [[http://www.linearcorp.com/|Linear]] [[http://www.linearcorp.com/radio_control.php#megacode|MegaCode series]].
@@ Line 87: / Line 87: @@
 But code protection is probably used.
 This chip can also come as One Time Programmable, and might be factory programmed.
+===== protocol =====
+The MegaCode protocol is partially specified in the [[https://apps.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=N&application_id=98433&fcc_id=EF4ACP00872|FCC]] documents [[https://apps.fcc.gov/eas/GetApplicationAttachment.html?id=112614|MegaCode1]] ({{:megacode:megacode_1.pdf|backup}}) and [[https://apps.fcc.gov/eas/GetApplicationAttachment.html?id=112615|MegaCode2]] ({{:megacode:megacode_1.pdf|backup}}).
+It uses Amplitude Modulation (AM) on 318MHz.
+There are two levels: on and off.
+The transmission uses 24 bit frames and 1 blank cell.
+Each is 6 ms long.
+Within each bit frame a 1 ms pulse is send.
+The pulse is either in the first or second half within the bit frame (after 2 or 5 ms).
+This defines if the bit is a 0 or 1.
+The first bit frame is used as sync frame and is always a 1.
+It is followed by 20 system code bits and 3 data bits.