CS4103 Datasheet, PDF (10/24 Pages) National Semiconductor (TI) – IEEE P1394a Physical Layer Device

Signal Definitions (Continued)
2.2.2 Transceiver/1394 Cable Connection Signals
Signal Name
Pin
Type Description
TPB[0:2]–
TPB[0:2]+
TPA[0:2]–
TPA[0:2]+
TPBIAS[0:2]
CPS
42, 49,
55
43, 50,
56
44, 51,
57
45, 52,
58
46, 53,
59
27
I/O Negative Differential Signals for Port 0-2 Cable Pair B
Differential signal skew should be minimized by matching trace lengths within
the TPA and TPB differential pairs. In addition, TPA pair trace lengths should be
matched as closely as possible to TPB pair trace lengths within a port. Imped-
ance discontinuities may be minimized by routing TP lines primarily on the top
layer of the PCB. TP signal traces should have an impedance of 55 ohms to
analog ground and the analog ground plane should be continuous under the
TP traces. Minimize stub length by placing termination networks as close to the
CS4103 as possible.
I/O Positive Differential Signals for Port 0-2 Cable Pair B
Refer to TPB[0:2]– signal description.
I/O Negative Differential Signals for Port 0-2 Cable Pair A
Refer to TPB[0:2]– signal description.
I/O Positive Differential Signals for Port 0-2 Cable Pair A
Refer to TPB[0:2]– signal description.
I/O Twisted Pair Bias for Port 0-2
Bias generator output and connection detect input for the ports. Increase the
PCB trace widths on this line.
I
Cable Power Status Input
This comparator input detects valid cable power at voltages greater than 7.5V
and sets the PS (cable power active) bit (Address 00h[7]) in the CS4103 base
register. Voltages below 7.5V clear the PS bit. This pin is connected to a 402K
1% resistor to cable power and an 80.6K 1% resistor to ground.
2.2.3 Clock/Crystal Connection and Reset Signals
Signal Name
Pin
Type Description
XI
XO
RESET#
76
I
Xtal In
Clock or crystal input connection 24.576 MHz (+/-100 ppm).
77
O Xtal Out
24.576 MHz crystal connection. If a clock is connected to XI, XO is discon-
nected.
78
I
Active Low Reset Input
This pin is connected to a 56K resistor to VDD and a 0.1 µF capacitor to ground
yielding a power-on reset of approximately 3 ms.
2.2.4 Power to/from Bus Signals
Signal Name
Pin
Type
PC[0:2]
23, 24,
I
25
Description
Power Class Indicator 0 (MSB) through 2 (LSB)
The PC[0:2] pins are strapped to indicate power consumed from or supplied to
the bus (see P1394a specification, Table 8-3). At power-on the PC pins are
read and the Pwr_class field (Address 04h[5:7]) is set. This value is transmitted
in the pwr field of Self-ID packet zero.
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