Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2000-10-26
2002-04-30
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S379000, C327S001000, C326S021000
Reexamination Certificate
active
06380767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a connection control circuit for connecting two devices through a serial interface, standardized according to IEEE Standard for a High Performance Serial Bus, IEEE Std. 1394-1995, for example.
This application is based on a Japanese Patent Application No. Hei 11-306039 (unpublished), the content of which is incorporated herein by reference.
2. Description of the Related Art
Recently, considerations have been given to forming a network by connecting personal computers PCs, peripheral devices or audio-visual (AV) devices through serial interfaces (for example, according to IEEE Standard for a High Performance Serial Bus, IEEE Std 1394-1995, referred to as 1394-standard hereinbelow).
FIG. 11
shows a configuration of a network connected to four devices (referred to as nodes hereinbelow).
As can be seen in
FIG. 11
, a network is formed by interconnecting the nodes A, B, C, D by way of ports (
1
), (
2
) and (
3
). In the physical layer of each node A-D, there are provided a state arbitration machine
101
for initializing bus lines and securing the transmission right for bus lines, and a connection state managing machine (indicated by
5
in
FIG. 12
) provided in each port for managing port-to-port connections.
Each port (
1
)-(
3
) functions as a connection control circuit, and is comprised by a sending code processing circuit
1
, a sending circuit
2
, a receiving circuit
3
, a receiving code processing circuit
4
and a connection state managing machine
5
, as shown in FIG.
12
.
FIG. 12
shows a connection between the ports of two opposing nodes A, D of a transmission line, and in this case, port (
3
) of node A is connected to port (
1
) of node D.
Here, the operation of port-to-port connection within a given port is specified by a respective connection state managing machine
5
provided in each of the ports (
1
)-(
3
).
FIG. 13
shows a current state of the connection state managing machine
5
and its transition paths of connecting states.
First, when there is no node connection to the ports, the connection state managing machine
5
is in the disconnected state P
0
. While the machine is in state P
0
, if a new connection is made to its port, the state shifts to the resuming state P
1
, and the sending code processing circuit
1
and the receiving code processing circuit
4
inside the port are initialized. After the initialization step, the state shifts to the active state P
2
.
If a disconnection of a port is detected, the connection state managing machine
5
shifts to the disconnected state P
0
via the suspended state P
5
. Also, when the command is received from the upper layer to suspend a port, the state shifts from the active state P
2
to the suspended state P
5
. Further, when a port-disable command is received from the upper layer, the state shifts to the disabled state.
The disconnected state P
0
means physical and logical non-connections, and active state P
2
means physical and logical connections. The suspended state P
5
means a physical connection but no logical connection, and the disabled state P
6
means that the circuits are stopped within the port and that neither physical nor logical connection has been detected.
The manner of detecting the physical connection and logical connection is different depending on the type of serial-bus interfaces used to make the connection, i.e., whether the connection is the DC (direct current) coupling system (specified by P1394a Draft Standard for a High Performance Serial Bus) or the AC (alternating current) coupling system (specified by P1394b Draft Standard for a High Performance Serial Bus).
In the case of the DC coupling system, determination of physical and logical connections are made by detecting the voltage levels. The present invention is concerned with the AC coupling system so that detailed explanation of DC coupling system is omitted. The method of detecting physical and logical connections in the AC coupling system will be explained in the following.
In the AC coupling system, the physical connection is detected by utilizing a connection managing control signal called a tone signal. As shown in
FIG. 14
, a tone signal is a on/off modulated signal operating at a carrier clock frequency of 50 MHz with a period of 42.666 ms. Tone signals are transmitted when the port is either in the disconnected state P
0
or in the suspended state P
5
.
Only the envelope-signal part of the tone signal received by the receiver side is output from the receiving circuit
3
as sgd-signal (meaning signal detected). Upon receiving the tone signal, the connection state managing machine
5
recognizes that a physical connection has been made to its port based on the receipt of the sgd-signal.
On the other hand, when the nodes are connected to each other and both ports are in the active state P
2
(i.e., logically connected), signals from the state arbitration machine
101
of each node are transmitted to the sending code processing circuit
1
in each port, and a continuous signal is output from the sending circuit
2
. Here, a continuous signal means a random signal containing no long strings of ‘0s’ or ‘1s’, such that ‘0’ and ‘1’ are output in a ratio of 1:1 within a specific interval.
When the continuous signal is received by the receiver side, sgd-signal becomes fixed at ‘1’. When this state is detected, the connection state managing machine
5
recognizes that a logical connection is being made.
For the purpose of explaining the actions of the connection state managing machine
5
when it receives a tone signal or a continuous signal, it is assumed that the port is currently in the suspended state P
5
. When the connection state managing machine
5
is in the suspended state P
5
, and a tone signal is received, the current state is maintained, but if a continuous signal is received, the connection state managing machine
5
shifts to the resuming state P
1
. When neither the tone signal nor the continuous signal is being received, it is determined that the cable is not connected, and it shifts to the disconnected state P
0
.
FIGS. 15A and 15B
show flowcharts of the operations of the connection state managing machine
5
when the port starts from the suspended state P
5
.
FIG. 15A
shows the process of latching the envelope-signal sgd (the first signal) and producing an sdd-signal (meaning sd_detected, the second signal), and
FIG. 15B
shows the process of setting ‘1’ in the rok-signal (meaning receive OK) when a continuous signal is detected. Processes described in
FIGS. 15A
,
15
B are carried out concurrently. The operations shown in
FIGS. 15A
,
15
B will be explained further in the following.
When the sgd-signal is received during the A-interval shown in
FIG. 14
, because sgd is set to ‘0’, sdd is also ‘0’ and the processing loop L
51
is carried out (step S
111
, S
112
). In the B-interval in the meantime, because sgd=‘1’ (step S
101
), latched signal sdd is also ‘1’ (step S
102
, processing
1
). Because the latched signal sdd is set to ‘1’, the sdd-signal passes through the loop processing L
51
(shown in
FIG. 15B
) and loop processing L
52
(step S
113
, S
114
) is carried out until the count
1
reaches a value of Tc. Here, Tc represents a count value corresponding to a time interval (666 &mgr;s) during which tone signal is ‘1’.
After an interval of Tc, sdd-signal is reset to ‘0’ (step S
115
, processing
2
). And, because a time interval Tc has elapsed since sgd was set to ‘1’, sgd-signal is reset to ‘0’, and therefore, sdd-signal maintains the reset state at ‘0’ (step S
115
, processing
2
), so that sdd-signal returns to the initial processing by way of the return path R
51
(step S
116
). While the tone signals are received, the above process is repeated and the port is maintained in the suspended state P
5
.
On the other hand, if a continuous signal is received from the opposing port, sgd-signal is fixed at ‘1’ (
FIG. 16
, interval C). In this case, sgd=‘l’ and sdd-signal is set to ‘1’ by pro
Nyu Takayuki
Suzuki Kohichiro
Cunningham Terry D.
Dickstein , Shapiro, Morin & Oshinsky, LLP
NEC Corporation
Nguyen Long
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