Siemens KNX EIB TP-UART 2-IC Manual page 20

GAMMA instabus
Release: February 2012
KNX EIB TP-UART 2-IC
3.2 UART – Interface to host controller
3.2.1 Configuration and Timing
The TP-UART-IC has a full duplex UART-interface to transmit and receive KNX frames
asynchronously. The baud-rate depends on the setting of BDS pin (9600 or 19200). The frame format
consists of a start bit (=0), eight data bits (LSB first), an even parity bit and one stop bit (=1)
logical
value
1
Start
bit 0
Bit (0)
0
LSB
Fig. 2: UART Interface
The parity bit of every received byte from the host will be checked by the TP-UART. Errors will be
reported to the host controller. Erroneous bytes (faulty parity) from EIB receiver will be checked too, but
the host won't be informed. In those cases the host controller has to recognize the parity faults in the
transmitted telegrams by its own. The UART receiver accepts frames up to a maximum baud rate
deviation of 3%.
3.2.2 Resetbehavior
After connecting the
(level 0 V) at pin RESn. This is valid for all modes. If Normal Mode is activated the following will
happen at the UART-interface.
TxD will be 0 as long as there was no bus signal on the EIB for 40 Tbit (1 Tbit = 1/9600 s; Attention:
The bittime of RxD/TxD depends on the adjusted baud rate at the UART-interface, for example 1 Tbit
or 0,5 Tbit). This results in a complete time of 40 Tbit + 12 Tbit = 5,42 ms. Then TxD changes for 1
Tbit to 1 and following the service TP-UART-Reset.Indication is transmitted. This signal behavior on
TxD appears after each reset.
3.2.3 UART-Protocol Definition
The protocol between TP-UART-IC and the application controller is a two wire protocol with software
handshake. Each data byte transmitted to the TP-UART-IC is started with a control byte. Each data
byte received on the EIB is transparently transmitted through the TP-UART-IC and is therefore started
with the EIB control field. Additional Information from the TP-UART-IC is transmitted with an ESC code
on the EIB control field. The host controller which is connected to the TP-UART-IC needs either to
detect a receive time-out of 2 to 2,5 ms to detect an end of Packet or check the CRC16-CCITT.
3.2.3.1 Services to UART
The following Services are supported from the TP-UART-IC.
• U_Reset.request
• U_State.request
• U_ActivateBusmon
• U_AckInformation (Nack, Busy, Addressed)
• U_ProductID.request
Technical Manual
page 20
Serial
Character
operating voltage the
© Siemens AG 2012
Subject to change without further notice.
Parity
Stop
Bit
bit 7
Bit (0)
Bit (1)
(even)
MSB
TP-UART-IC generates
pages 42
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