User Manual
GAMMA instabus
Release: February 2012
KNX EIB TP-UART 2-IC
Siemens AG pages 42 Technical Manual
Infrastructure and Cities Sector,
Building Technologies
Control Products and Systems © Siemens AG 2012 page 15
P. O. Box 10 09 53, Subject to change without further notice.
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2.2.13 Transmit Pin TxO
The transmit pin is connected to VB+ via external resistor of typ. 68 Ω.
Symbol Parameter Min Max Unit Note
dV
BUS
delta(V
BUS
) during active LOW pulse -6 -9 V 1)
1) related to VB+
Table 14 Transmit Pin TxO
2.2.14 Supply Pin VIF
The Pin VIF is used as supply voltage for the pins TxD, RxD, RESn, SAVE, TSTOUT_TW, X1, X2 and
determines their high input or output level.
Symbol Parameter Min Max Unit
Note
V
IF
external supply voltage for interface 3.0 5.5 V 1)
C
VIF
external decoupling capacitor 10 nF 2)
1) typical supply voltages: 3.3 V or 5 V
2) recommended; should be placed as close as possible between VIF and adjacent VB- device pins.
Table 15 Supply Pin VIF
2.2.15 Oscillator Pins X1 and X2
The oscillator Pins X1 and X2 are used for directly connecting a crystal of 4.9152 MHz without
additional external capacitors. The tolerance of the oscillator is set by the parameters of the external
crystal, and is expected to be +/- 0.05 %.
It is possible to drive the ASIC by an external clock by forcing the X1 with the external clock; pin X2
must be open
In Analog Mode no external XTAL is needed and the XTAL oscillator does not run. In this case X1
must be connected to VIF or VB-, X2 must be open.
Symbol Parameter Min Max Unit Note
V
X1/2
Oscillator voltage at X1 and X2 -0.5 VIF + 0.5 V
V
IL
voltage range for input low level 0.3 * VIF
V
IH
voltage range for input high level 0.7 * VIF
f
clk
clock frequency for external clock 2.4576 4.9152 MHz 1)
1) 4.9152 MHz or 2.4576 MHz, no other clock frequencies
Table 16 Oscillator Pins X1 and X2
2.2.16 Interface Pin RxD
The UART interface input pin RxD receives the information from host electronic to control the
transmitter of the ASIC. This pin is an input pin with pull-down resistor. The switching levels are derived
from external supply voltage VIF.
In normal mode: RxD = LOW RxD3 = HIGH transmitter switches on
In analog mode: RxD = HIGH RxD3 = HIGH transmitter switches on