410 Chapter 14
Picture information or even the entire picture can be
lost if any vital data is missing with digital video inter-
faces. DVI cable and its termination are very important
and the physical parameters of the twisted pairs must be
highly controlled as the specifications for the cable and
the receiver are given in fractions of bit transmission.
Requirements depend on the clock rate or signal
resolution being used. Transferring the maximum rate
of 1600 × 1200 at 60 Hz for a single link system means
that one bit time or 10 bits per pixel is
or 0.606 ns.
The DVI receiver specification allows 0.40 × bit
time, or 0.242 ns intrapair skew within any twisted pair.
The pattern at the receiver must be very symmetrical.
The interpair skew, which governs how bits will line up
in time at the receiving decoder, may only be 0.6 × pixel
time, or 3.64 ns. These parameters control the transmis-
sion distances for DVI.
Also, the cable should be evaluated on its insertion
loss for a given length. DVI transmitter output is speci-
fied into a cable impedance of 100: with a signal
swing of ±780 mV with a minimum signal swing of
±200 mV. When determining DVI cable, assume
minimum performance by the transmitter—i.e.,
200 mV—and best sensitivity by the receiver which
must operate on signals ±75 mV. Under these conditions
the cable attenuation can be no greater than 8.5 dB at
1.65 GHz (10 bits/pixel × 165 MHz clock) which is
relatively difficult to maintain on twisted-pair cable.
DVI connections combine the digital delivery,
described above, with legacy analog component
delivery. This allows DVI to be the transition delivery
scheme between analog and digital applications.14.9.3.2 HDMIHDMI (high definition multimedia interface) is similar
to DVI except that it is digital-only delivery. Where DVI
has found its way into the commercial space as well as
consumer applications, HDMI is almost entirely con-
sumer-based. It is configured into a 19 pin connector
which contains four shielded twisted pairs (three pairs
data, one pair clock) and seven wire for HDCP (copy
protection), devices handshaking, and power. The stan-
dard versions of HDMI are nonlocking connector, attest-
ing to its consumer-only focus.14.9.3.3 IEEE -1394 or FireWire Serial DigitalFireWire, or IEEE -1394, is used to upload DV, or digital
video, format signals to computers etc. DV, sometimes
called DV25, is a serial digital format of 25 Mbps. IEEE
1394 supports up to 400 Mbps. The specification defines
three signaling rates, S100 (98.304 Mbps), S200
(196.608 Mbps), and S400 (393.216 Mbps).
IEEE 1394 can interconnect up to sixty three devices
in a peer-to-peer configuration so audio and video can
be transferred from device to device without a computer,
D/A, or A/D conversion. IEEE 1394 is hot plugable
from the circuit while the equipment is turned on.Table 14-13. Comparing Twisted-Pair High-Frequency Formats
Standard Format Intended
UseConnector
StyleCable Type Transmission
Distance^1Sample
RateData Rate
(Mbps)Guiding
DocumentD1 component parallel broadcast multipin D multipairs 4.5 m/15 ft 27 MHz 270 ITU-R BT.601-5
DV serial professional/
consumer(see IEEE 1394) 4.5 m/15 ft 20.25 MHz 25 IEC 61834IEEE 1394
(FireWire)serial professional/
consumer1394 6 c o n d u c t o r s ,
2-STPs/2 pwr4.5 m/15 ft n/a 100, 200, 400 IEEE 1394USB 1.1 serial consumer USB
A & B4 conductors,
1 UTP/ 2 pwr5 m/16.5 ft n/a 12 USB 1.1
Promoter Group
USB 2.0 serial professional/
consumerUSB
A & B4 conductors,
1-UTP/ 2 pwr5 m/16.5 ft n/a 480 USB 2.0
Promoter Group
DVI serial/
parallelconsumer DVI
(multipin D)Four STPs 10 m/33 ft To 165 MHz 1650 DDWG; DVI 1.0HDMI parallel consumer HDMI (19 pin) Four STPs +
7 conductorsUnspecified To 340 MHz To 10.2 Gbps HDMI LLCDisplayPort parallel consumer 20 pin Four STPs +
8 conductors15 m To 340 MHz To 10.8 Gbps VESA(^1) Transmission distances may vary widely depending on cabling and the specific equipment involved.
STP = shielded twisted pair, UTP = unshielded twisted pair, n/a = not applicable
0.1 1 165 MHz e