NCN51206GEVB Datasheet, PDF (33/55 Pages) ON Semiconductor – Transceiver for KNX Twisted Pair Networks

NCN5120
b (busy mode):
‘1’ if busy mode is active. Can be enabled with U_SetBusy.req (see Set Busy Service, p31) and
disabled with U_QuitBusy.req service (see Quit Busy Service, p31) or U_Ackn.req service
(see Receive Frame Service, p44).
aa (auto−acknowledge):‘1’ if auto−acknowledge feature is active. Can be enabled with U_SetAddress.req service
(see Set Address Service, p32).
ap (auto−polling): ‘1’ if auto−polling feature is active. This feature can be enabled with U_Configure.req service
(see Configure Service, p35).
c (CRC−CCITT): ‘1’ if CRC−CCITT feature is active. This feature can be enabled with U_Configure.req service
(see Configure Service, p35).
m (frame end with MARKER): ‘1’ when feature is active. This feature can be enabled with U_Configure.req service
(see Configure Service, p35).
Remarks:
• Set Address Service can be issued any time but the new physical address and the autoacknowledge function will only
get active after the KNX bus becomes idle.
• Autoacknowledge can only be deactivated by a Reset Service (p31)
• x = don’t care
• Dummy byte can be anything. NCN5120 completely disregards this information.
Set Repetition Service
Specifies the maximum repetition count for transmitted frames when not acknowledged with IACK.
Separate counters can be set for NACK and BUSY frames. Initial value of both counters is 3.
If the acknowledge from remote Data Link Layer is BUSY during frame transmission, NCN5120 tries to repeat after at least
150 bit times KNX bus idle. The BUSY counter determines the maximum amount of times the frame is repeated. If the BUSY
acknowledge is still received after the last try, an L_Data.con with a negative conformation is sent back to the host controller.
For all other cases (NACK acknowledgment received, invalid/corrupted acknowledge received or time−out after 30 bit
times) NCN5120 will repeat after 50 bit times of KNX bus idle. The NACK counter determines the maximum retries.
L_Data.con with a negative confirmation is send back to the host controller when the maximum retries were reached.
In worst case, the same request is transmitted (NACK + BUSY + 1) times before NCN5120 stops retransmission.
Host Ctrl
NCN5120
U_SetRepetition.req
11110010
KNX Bus
Maximum Repetitions
0bbb0nnn
Dummy
xxxxxxxx
Dummy
xxxxxxxx
Figure 38. Set Repetition Service
bbb: BUSY counter (a frame will be retransmitted bbb−times if acknowledge with BUSY).
nnn: NACK counter (a frame will be retransmitted nnn−times if acknowledge with NACK).
Remark: Bit 3 and 7 of the second byte need to be zero (‘0’)!
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