Cryptography – Communication system using cryptography – Wireless communication
Reexamination Certificate
1998-12-08
2002-05-07
Barron, Jr., Gilberto (Department: 2132)
Cryptography
Communication system using cryptography
Wireless communication
C380S268000, C380S261000
Reexamination Certificate
active
06385319
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an encoding circuit used in a serial bus (for example, a serial bus standardized by the Institute of Electrical and Electronics Engineers [IEEE] Standard for a High Performance Serial Bus—the IEEE Std 1394-1995-, hereafter called a 1394) connectable to a personal computer (hereafter, a PC) and electronic devices.
A network using a 1394 for the purpose of transmitting a control signal and a main signal between a PC and peripheral devices such as a printer, a hard disk, a scanner and the like, or between a PC and an AV (Audio Visual) electronic device (hereafter, call a 1394-equipped terminal device a node) is supposed.
A node has a port (hereafter, called a DS port) using an encoding method of transmitting a data signal and a strobe signal at the same time, which is called a DS-Link encoding method (making reference to the IEEE Std. 1394-1995 pp.34). The DS-Link encoding method has a characteristic that a clock can be regenerated by generating an exclusive OR of two (2) signals on the receiving side on the one hand, but it has also a defect, on the other hand, that a transmitting signal transmitted from a transmitting node can not be regenerated precisely on the receiving side in the case where a phase difference between two signals is generated on the receiving side due to a difference between propagating speeds of the two signals because two signals are transmitted at the same time and in the case where a distance between nodes becomes long. Therefore, a distance between nodes is limited within several meters in the case where a DS-Link encoding method is used.
On the other hand, in the case where a distance between nodes extends over for scores of meters, a node has a port (hereafter, called a serial port) having an encoding circuit for the purpose of performing a serial transmission. However, in this case, it is necessary to regenerate a clock out of a transmission signal using a clock recovery circuit on the receiving side.
In
FIG. 6
, a constitution of nodes having DS ports and serial ports are shown. The port (a)s, (b)s are DS ports, and the port (c)s is serial ports. The present invention relates to a serial port, description about a DS port is omitted (making reference to the IEEE 1394-1995 pp. 76 in detail). As for the node A and the node B, serial ports are connected to each other by way of a transmission path. Each node has the network initiation/control state machine
21
performing the acquisition of the transmission right to the network at the time of the initiation of the network and during the usual operation. A serial port is composed of the transmitting block
18
, the receiving block
19
and thee port initiation block
20
.
The transmitting block
18
transmits a control signal outputted from the port initiation block
20
until the initiation of the port is completed. After the completion of the initiation of the port, the transmitting block
18
transmits a control signal outputted from the network initiation/control state machine.
The receiving block
19
passes a received control signal to the port initiation block
20
until the initiation of the port is completed. The receiving block
19
passes a control signal to the network initiation/control state machine after the completion of the initiation of the port.
The port initiation block
20
acknowledges that ports were connected to each other using a Port_Status signal at the time when the initiation of the ports was completed and a communication connecting the ports to each other could be available to the upper network initiation/control state machine
21
. The network initiation/control state machine
21
which has detected a change of a Port_Status signal starts the initiation of the network by transmitting a bus reset signal. The present invention relates to a serial port., description about the initiation of the network is omitted (making reference to the IEEE 1394-1995 pp. 98-112 in detail).
The operation procedure of the port initiation block
20
is shown in FIG.
7
. The transmitting block operates at S
100
(baud rate 125 Mb/s) of the lowest transmitting speed at the initiation of the ports. Until an output clock of a PLL (Phase Locked Loop) circuit generating a transmitting clock is stabilized (locked) at 125 MHz after the power of the nodes is switched on, since the transmitting block remains in a state of resetting, there is no output from the port. Once an output of the transmitting PLL is stabilized, the port initiation block
20
outputs a Request/Grant code (0001) in series as a control signal. A list of control signal codes is shown in
FIG. 8. A
opposed node also operates in the similar procedure, receives a Request/Grant code from the other opposed node. Upon receiving a Request/Grant code, in the receiving block, a clock recovery circuit generating a receiving clock out of a received signal starts to retract a signal, and waits for being capable of stably generating (locking) a receiving clock. After a clock recovery circuit is locked, detecting a boundary of a block code out of a signal serial-transmitted is performed. After the detection of a boundary of a block code, the synchronization between a scrambler which is located in the receiving block of the opposed node and a descrambler (for example, in
FIG. 6
, the scrambler of the node A and the descrambler of the node B, or the scrambler of the node B and the descrambler of the node A) is obtained. After the establishment of the synchronization between a scrambler and a descrambler, an IDLE code (0000) is outputted as a control signal from the port initiation block. The node which has detected an IDLE code recognizes that a clock recovery circuit of the opposed node being locked, the detection of a block code boundary and the establishment of the synchronization between a scrambler and a descrambler are completed.
Next, in order to arbitrate a transmitting speed between ports, the port initiation block
20
outputs a SPEED code indicating the maximum transmitting speed that its port can transmit as a control signal. After receiving a SPEED code from the opposed node, the port initiation block
20
compares the SPEED code from the opposed node with the SPEED code transmitted by itself, and sets a transmitting speed of the ports at the lower transmitting speed. At that time, in the case where the transmitting speed is set at S
100
(a plurality of transmitting speeds are standardized by the IEEE 1394, the lowest transmitting speed is defined as S
100
:100 Mb/s. Besides this, S
200
: 200 Mb/s, S
400
:400 Mb/s and the others are standardized.), a Port_Status signal is set in order to acknowledge the completion of the initiation of the port to the upper network initiation/control state machine. In the case where the transmitting speed is not set at S
100
, a speed arbitration flag indicating the completion of the arbitration of a transmitting speed is set, and after a transmitting PLL circuit and a clock recovery circuit are reset, the procedure of the initiation of the port is performed again. After the completion of the steps up to the establishment of the synchronization between a scrambler and a descrambler, a Port_Status signal is set, then, the initiation of the port is completed.
For example, if the maximum transmitting ability of the node A is S
100
and the maximum transmitting ability of the node B is S
200
, the node A transmits a code indicating that the maximum speed of the node A is S
100
, the node B transmits a code indicating that the maximum speed of the node B is S
200
. In the node B, as a SPEED code received from the node A is recognized, a transmitting speed of the serial port of the node B is set at S
100
. Since both the node A and the node B already operates at S
100
, the operations of the node A and the node B subsequently transfer to the usual operations. On the other hand, in the case where the maximum transmitting speed is set at S
200
in both the node A and the node B, a transmitting speed of the serial port of both the node A a
Barron Jr. Gilberto
NEC Corporation
Smithers Matthew
Sughrue & Mion, PLLC
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