MSC8154E Datasheet, PDF (58/68 Pages) Freescale Semiconductor, Inc – Quad-Core Digital Signal Processor with Security

Hardware Design Considerations
3.4 SGMII AC-Coupled Serial Link Connection Example
Figure 39 shows an example of a 4-wire AC-coupled serial link connection. For additional layout suggestions, see AN3556
MSC815x High Speed Serial Interface Hardware Design Considerations, available on the Freescale website or from your local
sales office or representative.
SR[1–2]_TX[[1–2]
50 Ω
Transmitter
50 Ω
SGMII
SerDes Interface
SR[1–2]_TX[1–2]
SR[1–2]_RX[1–2]
50 Ω
Receiver
SR[1–2]_RX[1–2]]
50 Ω
C_TX ^{SR[1–2]_RX[1–2]}
SR[1–2]_RX[1–2]
50 Ω
Receiver
C_TX
50 Ω
C_TX
50 Ω
SR[1–2]_TX[1–2]
Transmitter
C_TX
50 Ω
SR[1–2]_TX[1–2]
Figure 39. 4-Wire AC-Coupled SGMII Serial Link Connection Example
3.5 Connectivity Guidelines
Note: Although the package actually uses a ball grid array, the more conventional term pin is used to denote signal
connections in this discussion.
First, select the pin multiplexing mode to allocate the required I/O signals. Then use the guidelines presented in the following
subsections for board design and connections. The following conventions are used in describing the connectivity requirements:
1. GND indicates using a 10 kΩ pull-down resistor (recommended) or a direct connection to the ground plane. Direct
connections to the ground plane may yield DC current up to 50 mA through the I/O supply that adds to overall power
consumption.
2. V_DD indicates using a 10 kΩ pull-up resistor (recommended) or a direct connection to the appropriate power supply.
Direct connections to the supply may yield DC current up to 50 mA through the I/O supply that adds to overall power
consumption.
3. Mandatory use of a pull-up or pull-down resistor is clearly indicated as “pull-up/pull-down.” For buses, each pin on
the bus should have its own resistor.
4. NC indicates “not connected” and means do not connect anything to the pin.
5. The phrase “in use” indicates a typical pin connection for the required function.
Note: Please see recommendations #1 and #2 as mandatory pull-down or pull-up connection for unused pins in case of
subset interface connection.
MSC8154E Quad-Core Digital Signal Processor with Security Data Sheet, Rev. 0
58
Freescale Semiconductor