KR20000055575A - Method for arbitrating asynchronous packet in bus system - Google Patents

Abstract

PURPOSE: A method for arbitrating an asynchronous packet in a bus system, is provided to reduce waste of bandwidth by substituting arbitration reset gap for new sub-action gap to efficiently transmit data on 125-micro seconds, when nodes connected to the bus system are few after adding the new sub-action gap. CONSTITUTION: A method for arbitrating an asynchronous packet in a bus system, performing fair arbitration to transmit the asynchronous packet among optional nodes comprises the steps of: deciding whether an acknowledge packet is received to decide a starting time of arbitration for transmitting the asynchronous packet; if so, performing arbitration after a bus is idled during new sub-action gap.

Description

A method for arbitrating Asynchronous Packet in bus system {method for arbitrating Asynchronous Packet in bus system}

TECHNICAL FIELD The present invention relates to a bus system, and more particularly, to an Asynchronous Packet arbitration method in a bus system.

In recent years, the demand for a high-speed interface in digital devices has brought a lot of attention to the IEEE 1394 serial bus, which is why it is widely applied to a variety of digital devices, especially digital audio / video.

The IEEE 1394 serial bus features up to 63 digital devices on a single bus and has an isochronous data communication mode suitable for various topologies and real-time data transfers. It has many features.

The transfer of data, rather than the transmission time, such as Control and transaction set, Printer transfer data, Still camera image data, etc. on the IEEE 1394 serial bus In order to ensure reliability, data for which retry transmission is to be supported is transmitted in an Asynchronous packet structure.

Real-time data in which time is important is transmitted in an isochronous packet structure, which means that late data is meaningless and retry transmission because transmission time must be guaranteed. This is not supported.

Hereinafter, an isochronous / asynchronous packet arbitration method in a bus system according to the prior art will be described with reference to the accompanying drawings.

1 is a diagram illustrating a relationship between 1394 serial bus protocol layers according to the prior art, which includes serial bus management (hereinafter, referred to as SBM) 11, a physical layer 12, and Link layer 13, A / V CIP layers 14, Application layer, Transaction layer 16, Plug control register (Plug Control Register) 17, Connection Management Protocol section 18, Function Control Protocol section 19, and audio / video control command and transaction set (AV / C) Command and Transaction Set) and SBP-2 (20).

2 illustrates a 1394 serial bus cycle structure according to the related art.

The operation of an isochronous / asynchronous packet arbitration method in a bus system according to the related art configured as described above will be described in detail with reference to the accompanying drawings.

First, the IEEE 1394 serial bus supports two transmission schemes: isochronous packet transmission and asynchronous packet transmission. Arbitration is used to transmit packets to the bus. The way is different.

The isochronous packet transmission uses an isochronous arbitration method, and the asynchronous packet transmission is a pair and an immediate arbitration. Use the method.

In order to transmit a cycle start packet, the root node transmits the packet using Cycle_Master Arbitration.

As shown in FIG. 2, the isochronous packet transmission is a cycle master (Cycle) that exists only on a bus according to a cycle synch generated at predetermined intervals (8 ms and 125 ms). This is done by transmitting a cycle start packet in the master.

When the transmitting node of the isochronous communication receives the cycle start packet, the bus is idled by an isochronous gap, and then initiates an arbitration. Take ownership of

Subsequently, the transmitting node of the isochronous communication performs isochronous packet transmission using a channel and bandwidth previously allocated by an isochronous resource manager (IRM). In the beginning, while the channel and the bandwidth (channel and bandwidth) is allocated, the packet transmission is guaranteed through the ablation every 125 ms cycles.

After the packet has been transmitted, all other nodes on the bus have the same channel number as the channel set in the header of the transmitted isochronous packet of their isochronous receive port registers. If you have one, receive it.

If there is another node that wants to send isochronous packets, wait for the isochronous gap as above, and then start abiting to acquire ownership of the bus. The isochronous packet is transmitted using a channel and bandwidth.

In such isochronous packet transmission, the period in which the isochronous packet can be transmitted in the nominal cycle time is about 100 ms.

Restricting the isochronous packet transmission to 100 ms is because the isochronous packet transmission is higher in priority than the asynchronous packet transmission, so the isochronous packet transmission is isochronous. This is to prevent Starvation from transmitting the packet exclusively to the bus and thus preventing the transmission of Asynchronous Packets.

The isochronous packet transmission is an isochronous packet using all bandwidths corresponding to 100 ms according to the bandwidth allocated by a node during a 100 ms period. ) Can be transferred.

In addition, the cycle start packet transmitted by the cycle master has the highest priority in the arbitration, so it is transmitted first. To do this, the route is always transmitted first. Cycle Master).

On the other hand, as for the acronym communication, after the isochronous communication (maximum period 100ms) is completed during the nominal cycle time, the bus is idled during the subaction gap (1ms ~ 10ms). It starts after it enters Idle state.

The Asynchronous Packet transmission detects a Subaction Gap by specifying an address of a transmitting side and a receiving side node in an Asynchronous Packet Header, and then performs an Arbitration. Once the bus is licensed, it is sent to all other nodes on the bus.

Then, only a node having a destination address specified in the transmitted packet header receives the transmitted Asynchronous Packet, and transmits the reception result to Actknowledge.

In order to transmit such Asynchronous Packets, Fair Arbitration is used. The reason for using Arbitration is that a node close to the root is always used because of the principle of Arbitration. Since it beats the arbitration, a section called a fair interval is set.

The reason for setting the Fair Interval section is that when a plurality of nodes participate in Arbitration of a bus during a Fair Arbitration period, the node acquiring the bus once has the ABIT. This is to ensure that all nodes that participate in the Arbitration take ownership of the bus and then participate in Arbitration again so that all nodes have equal access to the bus.

Here, the Fair Interval section is started by the nodes detecting the Arbitration Reset Gap (maximum 20ms) and setting the Arbitration enable bit. At this time, nodes that want to transmit an Asynchronous Packet participate in an arbitration and reset the Arbitration enable bit when the owner of the bus is acquired from a node close to the root. .

Nodes that do not acquire ownership of the bus in the arbitration may rejoin the arbitration after rejoining the arbitration if the bus becomes idle again during the subaction gap. Once ownership is obtained, the Arbitration reset bit is reset.

As a result, when all nodes attempting to acquire ownership of the bus in the pair interval interval succeed in arbitration, the fair arbitration ends.

Therefore, once a node that has taken ownership of a bus takes ownership of the bus again, after the bus is idle during the Arbitration Reset Gap, the node enables the Arbitration enable bit. This can be achieved by taking ownership of the bus after participating in an arbitration.

In this isochronous / asynchronous packet arbitration method in a bus system according to the prior art, a node that intends to transmit an asynchronous packet always idles the bus during a subaction gap. Since the transmission can be started after acquiring the bus after acknowledging the idle operation and obtaining the bus, it wastes a lot of bandwidth.

In addition, the bus is idle during the Arbitration Reset Gap, which is larger than the subaction gap in order for the node that once used the bus to support Fair Arbitration to use the bus again. Arbitration can be started after the Idle has been checked, so if you don't touch the number of nodes connected on the bus, especially if there are only a few nodes sending actual Asynchronous Packets over a period of time. If only the node transmits a high bandwidth Asynchronous Packet, such as bitmap data, there is also a problem of significantly reducing the efficiency of the bus.

Accordingly, the present invention has been made to solve the above problems, and when the number of nodes connected to the bus system is small by adding a new new_subaction gap, the new Woo into the Arbitration Reset Gap. An object of the present invention is to provide an asynchronous packet arbitration method in a bus system that uses a new_subaction gap.

1 illustrates a relationship between 1394 serial bus protocol layers according to the related art.

2 illustrates a 1394 serial bus cycle structure according to the prior art.

3 is a diagram illustrating an embodiment of fair arbitration of an Asynchronous Packet arbitration method in a bus system according to the present invention.

4 is a view showing an embodiment of a cycle structure of an Asynchronous Packet arbitration method in a bus system according to the present invention.

FIG. 5 is a diagram illustrating an embodiment for determining a new_subaction gap using an Acknowledge Packet of an Asynchronous Packet arbitration method in a bus system according to the present invention.

FIG. 6 illustrates an embodiment of an asynchronous subaction due to a new_subaction gap according to the present invention.

A feature of the Asynchronous Packet arbitration method in a bus system according to the present invention for achieving the above object is a pair for transmitting an Asynchronous Packet between nodes in an environment of the bus system. An Asynchronous Packet Arbitration Method In A Bus System Performing Fair Arbitration, In case a few nodes are connected to the bus system, the node receives the Asynchronous Packet from the node receiving the Asynchronous Packet. Determining whether to receive an Acknowledge Packet by searching the code of the transmitted Acknowledge Packet, and if the Acknowledge Packet is received, a new_subaction gap during the gap), the bus is idled and then subjected to arbitration. There is.

The new_subaction gap confirms that the bus is idle after nodes recognize any Acknowledge Packet being transmitted to the bus and participates in the arbitration. It means Bus Idle Time to and has other features.

The new_subaction gap is a PHY Process Time, which is a time until the confirmation of the Arbitration enable bit and the PHY Arbitration Request, and the cuewood. It is another feature that is determined by the time to confirm the existence of a queued PHY Arbitration Request and the bus idle check time.

The new_subaction gap is characterized by having a smaller value than the conventional subaction gap.

The random node may set the new_subaction gap as an arbitration reset gap in the case of a bus system having a random number of 3 to 5 or less. Another feature is that it is programmed to do so.

Hereinafter, a preferred embodiment of an Asynchronous Packet arbitration method in a bus system according to the present invention will be described with reference to the accompanying drawings.

FIG. 3 is a diagram showing an embodiment of Fair Arbitration of an Asynchronous Packet Arbitration Method in a bus system according to the present invention, and FIG. 4 is a diagram of a bus system according to the present invention. FIG. 5 is a diagram illustrating an embodiment of a cycle structure of a synchronous packet arbitration method, and FIG. 5 is an actuation packet of an asynchronous packet arbitration method in a bus system according to the present invention. FIG. 6 is a diagram illustrating an embodiment for determining a new_subaction gap using a packet, and FIG. 6 is an asynchronous subaction caused by a new_subaction gap according to the present invention. Is an illustration of one embodiment of FIG.

Such asynchronous packet arbitration method in a bus system according to the present invention will be described in detail with reference to the accompanying drawings.

First, when a bus reset occurs, as shown in FIG. 1, the PHY of all nodes sets an arbitration enable bit to enable the node to be arbitrated. Notifies the link layer of the change to the state.

In addition, the root node determined at bus reset searches for the number of arbitrary nodes connected to the 1394 serial bus system and determines the size of the new new_subaction gap when the number of nodes is small (3-5 nodes). .

The new_subaction gap confirms that the bus is idle after nodes recognize any Acknowledge Packet being transmitted to the bus and participates in the arbitration. It means Bus Idle Time.

The new_subaction gap has a smaller value than the existing subaction gap.

After that, all nodes search for a bus to detect whether an Arbitration Reset Gap is detected, and when the Arbitration Reset Gap is detected, participate in Fair Arbitration. .

Subsequently, the node that acquires the bus by winning the fair arbitration transmits an Asynchronous Packet, and all nodes that do not acquire the bus by the fair arbitration are new_ After detecting whether a new_subaction gap is detected, and if detected, as shown in FIG. 3, the UE participates in an arbitration for transmitting an Asynchronous packet.

After all nodes have acquired the bus through this process, the Abitration to support Fair Arbitration through the Self-ID process, which is the final stage of the bus configuration. Set the Arbitration Reset Gap to the size of the new_subaction gap when the number of connected nodes is small according to the number of nodes connected on the bus. do.

Accordingly, in order to acquire a bus again, a node that has acquired a bus needs a PHY when the bus is idle during an arbitration reset gap or a new_subaction gap. Set the Arbitration enable bit and, if there is a PHY Arbitration Request, participate in the Arbitration to acquire the bus at least in the next cycle. .

In addition, all inactive nodes remain in an idle state until an internal or external event occurs, and all ports of the node transmit an idle arbitration signal ZZ.

The cycle master transmits on a bus on a cycle start packet according to a cycle synch that occurs every 125 ms.

In order for the cycle master to transmit a cycle start packet, the bus is idled during a new_subaction gap and then cycled through a cycle_master arbitration on the bus. It transmits a packet (Cycle Start Packet) on the bus, and since the root node becomes the cycle master, the cycle start packet is always guaranteed to be transmitted first after the cycle synch occurs.

When a cycle is generated, when a packet is being transmitted on the bus, as shown in FIG. 5, an acknowledgment packet is received and the bus is idle. After checking, that is, after the bus is idle during the new_subaction gap, a cycle start packet is transmitted.

Here, the new_subaction gap is the PHY Process Time, which is the time until confirmation of the Arbitration enable bit and the PHY Arbitration Request, and the cuewood. It is determined by the time of confirming the existence of the queued PHY Arbitration Request, and the bus idle confirmation time.

When receiving the Acknowledgment Packet, all nodes other than the node received in response to the Asynchronous Packet transmitted by the previous packet do not analyze the code of the Acknowledge Packet. Do not.

That is, the PI only reads an Acknowledgment Packet, but the Link Layer does not analyze the Acknowledge Packet.

Therefore, only after acknowledging Data_Prefix on the bus, acknowledgment of the Acknowledge Packet by acknowledging that Data_End comes after an 8-bit Acknowledge Code. You can do it.

This is possible because the length of the data in the Acknowledge Packet is fixed to 8 bits so that it can be distinguished from all other packets.

In addition, since the size of the Ack_gap (up to 50 ms) is several times smaller than the new_subaction gap between transmissions of the Acknowledge Packet, other Asynchronous Packet transmissions Can't interrupt.

In addition, in order for the Link Layer to transmit Asynchronous or Isochronous Packets, a Fair Arbitration Request or an Isochronous Arbitration Request is required. When it generates, the node queues it.

When the nodes are able to transmit Asynchronous Packets, as shown in FIG. 3, an Arbitration enable bit of the pie is set, and? After the cycle start packet and the isochronous packet are received as?, ??, ??, the bus is idle or random actuation during the new_subaction gap. After receiving the Packet and acquiring the bus (after the bus is idle during the new_subaction gap).

Thus, while the pi has a Queued PHY Arbitration Request, the bus is idle during the new_subaction gap or it may not receive any Acknowledge Packets. If it confirms, it can notify the link layer and send data to be transmitted.

In addition, if the bus hits during the Arbitration Reset Gap (or a new_subaction gap if the number of connected nodes is small), the pi sets the Arbitration enable bit. set) and notify that a gap is detected in the link layer.

The node that wins the Arbitraion resets the Arbitration enable bit and the next Arbitration Reset Gap (if the number of connected nodes is small, the new_ When a new_subaction gap} is detected, the bit is set to be able to participate in the arbitration by setting the arbitration enable bit again.

When the node to which the packet is to be transmitted does not acquire the bus in Arbitration and starts the process of receiving data, the pie clears all of its request flags, and the link layer ) Tells the bus that it is busy and tells it to send a new request.

When the node that has acquired the bus by winning the arbitration finishes the transmission, all signals are driven by ZZ (Hi-Impedance) to release the bus and the pi returns to the idle state.

During the packet reception, the link layer determines whether the packet is a cycle start packet and if it is necessary to send an isochronous packet, the pi is an isochronous abitation request ( Issue an Isochronous Arbitration Request.

This can be sent immediately once the pi has confirmed that the bus is idle (50ms max), so transmission is not interrupted by Asynchronous Packets.

In addition, during the packet reception, the link layer determines whether it is necessary to transmit an Acknowledge Packet, and if so, the pie is imitated when the bus enters an idle state (up to 50 ms). Implement an arbitration request.

FIG. 6 illustrates an Asynchronous Cronus Aaction that transmits an Asynchronous Packet due to a new_subaction gap by using an arbitrary Acknowledge Packet on the bus as described above. subactions).

As described above, in the method of arbitrating the Asynchronous Packet in the bus system according to the present invention, when the number of nodes connected to the bus system is small by adding a new new_subaction gap, the abitation reset is performed. By replacing the new_subaction gap with an Arbitration Reset Gap, the data can be efficiently transmitted over 125 ms, thereby reducing the waste of bandwidth.

Claims (5)

A method for arbitrating an Asynchronous Packet in a bus system that performs Fair Arbitration for transmitting an Asynchronous Packet between arbitrary nodes, Determining whether to receive an Acknowledge Packet to determine an arbitration start time for transmitting the Asynchronous Packet; If the acknowledgment packet is received as a result of the determination, performing the abitation after the bus is idle during the new_subaction gap. Asynchronous Packet Arbitration Method in System. The method of claim 1, The new_subaction gap confirms that the bus is idle after nodes recognize any Acknowledge Packet being transmitted to the bus and participates in the arbitration. Asynchronous Packet arbitration method in a bus system, characterized in that the bus idle time (Bus Idle Time). The method of claim 2, The new_subaction gap is PHY Process Time, which is the time to check the Arbitration enable bit and PHY Arbitration Request, and Queued PHY Arbitration Request Asynchronous Packet arbitration method in a bus system characterized in that it is determined by the time to confirm the existence of the bus idle (Bus Idle) confirmation time. The method of claim 1, The new_subaction gap has a value smaller than a conventional subaction gap, wherein the Asynchronous Packet arbitration method in a bus system. The method of claim 1, And performing an arbitration by setting the new_subaction gap to an arbitration reset gap if the number of random nodes is smaller than a reference value. Asynchronous Packet arbitration method in a bus system.