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ECE 412:
Microcomputer Laboratory
Lecture 13: Other Devices on the XUP Board
Lecture 13
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Objectives
• A whirlwind tour of the parts on the XUP board that
we haven’t used or talked about yet.
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Review Questions
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.
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Parts We’ll Cover
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•
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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.
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XUP Development System Block Diagram
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LM4550 codec
• The LM4550 was designed specifically to provide a high quality
audio path and provide all analog functionality in a PC audio
system.
• 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
capability.
• 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.
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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
hertz)
– 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.
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Stereo
Analog
Inputs
Stereo
Analog
Outputs
National LM4550 ADC/DAC
Serial
Data
Low-Pass
Filter
Analog-toDigital
Converter
Digital-toAnalog
Converter
Low-Pass
Filter
Lecture 13
Serial
Data
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More Specifics on LM4550VH ADC/DAC
• Both a stereo Analog-Digital Converter and a stereo DigitalAnalog Converter.
– 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
zeros.
– Serial digital PCM in/out
• Pulse-code modulation (PCM) is a digital representation of an analog
signal
• 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.
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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.
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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
edge.
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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
Access Controller)
• Set of control registers and protocol for accessing them
– Hardware Control (signal pins)
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Block Diagram
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Some Detailed Features
•
OSP: Optimal Signal Processing
– mixed-signal processing in improved receiver noise and cross-talk
performance.
– 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.
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Initialization Sequence
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Some Details on Initialization
• On power-up or hardware reset the LXT972A reads the
Hardware Control Interface pins and sets the MDIO registers
accordingly.
• The following modes are available using either Hardware
Control or MDIO Control:
– Force network link operation to:
•
•
•
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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
commanded.
• When auto-negotiation is enabled, the LXT972A begins the
auto-negotiation/parallel-detection operation.
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Link Establishment Overview
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Connectivity to the LXT972A
MDC: Management Data Clock. Clock for the MDIO serial data channel.
Maximum frequency is 8 MHz.
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Interfaces
• MDIO, MDC: MDIO management data line and clock
line
• 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
CRS.
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Interfaces II
• 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
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Interfaces III
• 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
packet
• TX_ER: Transmission error detected by transceiver
• TXD0-3: Data to transmit
– Again, some support 4- or 5-bit format
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Device Identifier
• 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
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Dallas Semiconductor DS2401
• The DS2401 enhanced Silicon Serial Number is a low-cost,
electronic registration number that provides an absolutely
unique identity.
• The DS2401 consists of a factory-lasered, 64-bit ROM that
includes a unique 48-bit serial number, an 8-bit CRC, and an 8bit 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
number.
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Next Time
• Final project kickoff
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