Samsung SCX-1100 Service Manual page 73

CIRCUIT DESCRIPTION
3-3-2-7 USB INTERFACE PART
1. USB function description
As the mode of implementing low cost express PC
Interface, USB was applied. At USB, PC plays the role of
route hub simultaneously by existing in the highest level as
the host. That is, the device supporting each USB is con-
nected centering on PC.
The device is available for Interface for the maximum of
127. USB cable is composed of total of a set of twisted pair
and 2 power lines. Cables have two types.
One is used for express transmission of 12Mbps and may
be extended as long as 5m. The part for implementing USB
function is included in S3C46MOX(Jupiter3).
For Interface of USB, pull-up of 15KΩ is interfaced to the
data line of high level instruments, and, among data lines
of lower level instruments, pull-up resistance of 1.5KΩ is
interfaced to any one.
At this time, D+ line is pulled up for Full Speed device, and,
for Low Speed device, D-line is pulled up. For upper level
instruments(Host, HUB) speed of device is classified inter-
faced to low level by detecting any one among D+ and D-.
If both lines are in the level of GND at the same time, device
is judged that low device is not interfaced. In the transmis-
sion mode of USB, there are
(1) Control transmission,
(2) Interrupt transmission,
(3) Bulk transmission, isochronous transmission.
Control transmission is for Host to find out configuration
information from USB device. This is conducted when
device is interfaced. Interrupt transmission is used when
small quantity of data is sent periodically. Interval value
may be known from device in the case of initial setting. Bulk
transmission is valid in case of trying to transmit data in
large quantities or in case of transmitting them accurately.
Isochronous transmission should be assured of bandwidth,
and is used when transmitting large quantities of informa-
tion. Data in voice is used where delay is not allowed but
small error is allowed. At USB coding mode and bit stup-
ping are being conducted. First, in case original data is 1,
bit shall not change, and only when original data is 001, it
shall be inverted. Only while data is 1, 1 and 0 shall be
repeated. Also, in case 1, original data, is continued in 6 bit,
0 shall be inserted, Also, in the 1st phase of packet, data in
the synchronized pattern shall be sent. About more
detailed information regarding USB, see http//:www.usb.org.
Repair Manual
3-14
2. operation description
This system, when Host and USB cables are connected,
and when +5V is detected in power detector inside chip
and Vbus(U15-98), 3.3V comes out through Pull-uP termi-
nal. This is also connected to D+ in pattern of hardware and
supports Full-speed. Utilizing Configuration Endpoint,
EPO, in USB controller, Plug & Play function is operated.
Exchange of information between PCs is accomplished
through D+(U15-95) and D-(U15-96) terminals. This termi-
nal decides transmission speed depending on connection
of regulator output in USB controller, and decides size of
signal following USB and SPFC. Signal of general D+ and
D- terminals are same as Figure 10-3.
D+
D-
- This Document can not be used without Samsung's authorization -
< Figure 10-3. USB Signal Line DIAGRAM >
Samsung Electronics