HFC-SUSB Cologne Chip AG, HFC-SUSB Datasheet - Page 71

• Manufacturer Part Number: HFC-SUSB
• Description: Isdn S/t HDLC Basic Rate Controller
• Manufacturer: Cologne Chip AG

863 C EC2
7.5
Figure 15: Auxiliary port circuitry
The auxiliary port of the HFC-S USB needs some additional circuitry to reduce power consumption in
Suspend Mode. To avoid floating inputs PORT_D[7:0] must be connected to GND over a resistor (R2).
Of course this is only possible if the auxiliary port is not used. In the example above PORT_D0 is used
for a LED. R1 is the usual resistor to limit the current through the LED. Additional a resistor parallel to
the LED (RD1) is required to reach high input level at the auxiliary port pin when the bus is not driving
out in Suspend Mode.
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U 1
H F C _S U S B
*
To save some resitors all unused PORT_D outputs can be connected to ground over the same
resistor. In this case the bits of the auxiliary port data register P_DATA corresponding to these
PORT_D output pins must be set to the same value to avoid a short circuit.
hint!
Auxiliary port circuitry
P O R T_D 7
P O R T_D 6
P O R T_D 5
P O R T_D 4
P O R T_D 3
P O R T_D 2
P O R T_D 1
P O R T_D 0
/ AU X_W R
/ AU X_R D
11
10
9
8
7
6
5
4
2
1
optional
R 1
D 1
R D 1
R 2
R 3
R 4
R 5
R 6
R 7
G N D
R 8
Part List
Name
R1
R2
R3
R4
R5
R6
R7
R8
RD1
D1
U1
Value
1M
1M
1M
1M
1M
1M
1M
1M
620
LED
HFC-S USB
Cologne
Chip
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