Lecture 13: Other Devices on the XUP Board
Lecture 13 1
• A whirlwind tour of the parts on the XUP board that
we haven’t used or talked about yet.
Lecture 13 2
Why is the YUV format used by the video decoder more
efficient than using an RGB format?
The efficiency of YUV versus RGB lies in the fact that YUV is basically a
compressed form of RGB. The encoding scheme takes advantage of the
fact that the human eye is more sensitive to changes in brightness than
changes in color. Therefore the YUV system gives more weight to the
brightness (luminance) value of pixels. In RGB format, each pixel is
required to have 3 bytes of information. In YUV format, only brightness
data is sent for each individual pixel. The color data is only sent in 2 bytes
for every-other pixel, and is shared between 2 neighboring pixels.
Therefore, each set of 2 pixels features two brightness values (1 for each
pixel) and 2 color values that are shared between the two, for a total of 4
bytes for 2 pixels. The same 2 pixels in RGB would take 6 bytes of space.
This compression scheme allows YUV to be more efficient than RGB.
Lecture 13 3
Parts We’ll Cover
• AC97 CODEC and stereo amp
• LXT972A Ethernet Transceiver
• DS2401 serial interface SN ROM
Also on XUP board:
• Serial ATA ports (Advanced Technology Attachment: hard disk
standard created to replace the parallel ATA)
• MGT transceivers
• Serial port
• USB 2.0 (used for programming at present)
• SystemAce (used for Linux file system)
We have documentation on these for anyone interested in using
them in a project.
Lecture 13 4
XUP Development System Block Diagram
Lecture 13 5
• The LM4550 was designed specifically to provide a high quality
audio path and provide all analog functionality in a PC audio
• It features full duplex stereo ADCs and DACs and analog mixers
with access to 4 stereo and 4 mono analog inputs.
• Each mixer input has separate gain, attenuation and mute
control and the mixers drive 1 mono and 2 stereo analog
outputs, each with attenuation and mute control.
• The LM4550 provides a stereo headphone amplifier as one of
its stereo outputs and also supports National’s 3D Sound stereo
enhancement and a comprehensive sample rate conversion
• The sample rate for the ADCs and DACs can be programmed
separately with a resolution of 1 Hz to convert any rate in the
range 4 kHz – 48 kHz.
• Sample timing from the ADCs and sample request timing for the
DACs are completely deterministic to ease task scheduling and
application software development.
Lecture 13 6
Review of Digital Sampling
Sampling is the process of converting a signal (for example, a
function of continuous time or space) into a numeric sequence
(a function of discrete time or space).
Basic Idea: If you take digital samples of an analog signal at a high
enough rate, it is possible to convert the stream of digital
samples back into an faithful copy of the original signal
Nyquist-Shannon Sampling Theorem:
• The theorem states, in the original words of Shannon (where he
uses "cps" for "cycles per second" instead of the modern unit
– If a function f(t) contains no frequencies higher than W cps, it
is completely determined by giving its ordinates at a series of
points spaced 1/(2W) seconds apart.
Lecture 13 7
National LM4550 ADC/DAC
Analog Digital-to- Data
Lecture 13 8
Lecture 13 9
More Specifics on LM4550VH ADC/DAC
• Both a stereo Analog-Digital Converter and a stereo Digital-
– One output directly connects to audio headphone amplifier
– Digital data is based on the Audio Code ’97 (AC97) standard
• 18-bit accuracy (both input and output)
– 20-bit fields in AC97 (format require unused bits to be filled with
– Serial digital PCM in/out
• Pulse-code modulation (PCM) is a digital representation of an analog
• Sample rate set by AC97 input and crystal frequency
– Supports sample rates of 4-48kHz
– XTAL_IN is 24.576 MHz
– 22kHz is “conventional” high end of human hearing range.
Lecture 13 10
AC97 Timing and Data
• Output frames
– 256 bits of data in a frame: 16-bit TAG slot, 12 20-bit data slots
– SDATA_IN: Serial data, an output of LM4550
• A new Output Frame is signaled with a low-to-high transition of SYNC.
• The LM4550 checks each Frame to ensure 256 bits are received. If a
new Frame is detected (a low-to-high transition on SYNC) before 256
bits are received from the old Frame then the new Frame is ignored.
Lecture 13 11
AC97 Timing and Data (cont’)
• SYNC is sampled with the rising edge of BIT_CLK.
• The first tag bit in the Frame (“Valid Frame”) should be
clocked from the controller by the next rising edge of
BIT_CLK and sampled by the LM4550 on the following falling
Lecture 13 12
Intel LXT972A Ethernet Transceiver
• 10/100 Mbit Dual-Speed Transceiver
– A single-port Fast Ethernet 10/100 Transceiver that supports 10
Mbps and 100 Mbps networks.
– It complies with all applicable requirements of IEEE 802.3.
– It can directly drive either a 100BASE-TX line (up to 140 meters) or
a 10BASE-T line (up to 185 meters).
• Supports either wired or fiber-optic Ethernet
– XUP board only supports wired connection
• Built-in LED drivers
– Allow easy connection of status LEDs to transceiver
• Two control options
– MII (Media Independent Interface) for control by a MAC (Media
• Set of control registers and protocol for accessing them
– Hardware Control (signal pins)
Lecture 13 13
Lecture 13 14
Some Detailed Features
• OSP: Optimal Signal Processing
– mixed-signal processing in improved receiver noise and cross-talk
– less computational logic than traditional DSP-based designs.
• When operating at 100 Mbps, the LXT972A continuously transmits and
receives MLT3 symbols.
– when not transmitting data, the LXT972A generates “IDLE” symbols.
• During 10 Mbps operation, Manchester-encoded data is exchanged.
– when no data is being exchanged, the line is left in an idle state. Link pulses
are transmitted periodically to keep the link up.
• The LXT972A provides both an MDIO interface and a Hardware
Control Interface for device configuration and management.
– supports the IEEE 802.3 MII Management Interface also known as the
Management Data Input/Output (MDIO) Interface. This interface allows
upper-layer devices to monitor and control the state of the LXT972A.
– provides a Hardware Control Interface for applications where the MDIO is
not desired. The Hardware Control Interface uses the three LED driver pins
to set device configuration.
Lecture 13 15
Lecture 13 16
Some Details on Initialization
• On power-up or hardware reset the LXT972A reads the
Hardware Control Interface pins and sets the MDIO registers
• The following modes are available using either Hardware
Control or MDIO Control:
– Force network link operation to:
• 100BASE-TX, Full-Duplex
• 100BASE-TX, Half-Duplex
• 10BASE-T, Full-Duplex
• 10BASE-T, Half-Duplex
– Allow auto-negotiation/parallel-detection
• When the network link is forced to a specific configuration, the
LXT972A immediately begins operating the network interface as
• When auto-negotiation is enabled, the LXT972A begins the
Lecture 13 17
Link Establishment Overview
Lecture 13 18
Connectivity to the LXT972A
MDC: Management Data Clock. Clock for the MDIO serial data channel.
Maximum frequency is 8 MHz.
Lecture 13 19
• MDIO, MDC: MDIO management data line and clock
• COLLISION: Collision Detected
– The LXT972A asserts its collision signal, asynchronously to
any clock, whenever the line state is half-duplex and the
transmitter and receiver are active at the same time.
• CARRIER_SENSE: Carrier Sense
– For 100BASE-TX links, a start-of-stream delimiter (SSD)
causes assertion of carrier sense (CRS).
– An end-of-stream delimiter (ESD) causes de-assertion of
Lecture 13 20
• RX_CLK: Clock for incoming data and control signals
– Use this clock to latch incoming data
– Will need to synchronize latched data to main system clock
• RX_DV: Indicates valid incoming data
• RX_ER: Invalid (error) data received from Ethernet
• RXD0-3: Bus for received data
– Normal operation: 4 bits of data at a time
– Hardware may support a 5-bit (Symbol) mode
Lecture 13 21
• TX_CLK: Clock for sending data to the chip
– Again, not synchronized to system clock
– An output of Ethernet transceiver
• TX_EN: Valid data being transmitted
– Drive this high continuously from first to last nibbles of a
• TX_ER: Transmission error detected by transceiver
• TXD0-3: Data to transmit
– Again, some support 4- or 5-bit format
Lecture 13 22
• Many devices require unique identifier, so-called
“silicon serial number”
• Example would be Ethernet 48-bit MAC address
• Minimum number of wires should be dedicated to the
infrequent access, ideally one (1-Wire Protocol)
• Concept: manipulating a single line precisely in time,
a user can activate, program, or read back a ROM
Lecture 13 23
Dallas Semiconductor DS2401
• The DS2401 enhanced Silicon Serial Number is a low-cost,
electronic registration number that provides an absolutely
• The DS2401 consists of a factory-lasered, 64-bit ROM that
includes a unique 48-bit serial number, an 8-bit CRC, and an 8-
bit Family Code (01h).
• Data is transferred serially via the 1-Wire® protocol that requires
only a single data lead and a ground return.
• Power for reading and writing the device is derived from the
data line itself with no need for an external power source.
• XUP boards have such a 64-bit, factory electronic registration
Lecture 13 24
• Final project kickoff
Lecture 13 25