JPS63290430A - Bus control system - Google Patents

Abstract

PURPOSE:To allow the mixture of a card supporting an old/new protocol by designating a data transfer mode from a master, and sending a transfer mode permission signal from a slave side so as to judge the propriety of response. CONSTITUTION:When a master 1 designates a 1-word data transfer mode to a slave 21, the slave 21 (supporting the one word data transmission) sends a data acknowledge signal DTACK, the transmission protocol is continued to start the one word data transmission. On the other hand, in designating the block data transmission mode, since there is no change in the data transmission mode permission signal PACK, the master 1 recognizes it that the slave 21 is incapable of transferring a data in this mode. Moreover, in designating the block transfer mode from the master 1 to the slave 22, the signal PACK is sent from the slave 22 to inform it that the data transmission is enabled.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a bus system to which a group of cards such as a bus master and a bus slave constituting a computer are connected, and relates to an improvement in bus control. It is something that is given.

<Prior Art> In a bus system in which a bus master and a bus slave are connected, when data is transferred using the VME bus, for example, protocols are set for single word data transfer and block data transfer. There is.

However, a bus cycle is initiated and the selected bus
If a slave does not support one of these protocols, it has a way to notify the bus master of this. When configuring a system in such an environment, the following steps were taken:

(1) Configure the system so that protocols used within the system do not mix.

(2) Allow protocols to be mixed, and change the protocol to be used, for example, depending on the address sent from the bus master.

The system was configured using these two methods.

<Problems to be solved by the invention> In the above two methods, for (1), only a limited protocol is used, so the cards that can be used on the system bus are limited, and card compatibility is Regarding (2), which cannot be maintained, there is a problem that software management becomes complicated because the protocol is changed depending on the sent address, and it is not possible to respond flexibly to changes in the system configuration.

Specifically, when a card designed to respond to single-word data transfers exists, and a card with a block data transfer mode is added due to system performance improvement requirements, the new card and the existing card cannot be connected. It was difficult to use them together.

The present invention is intended to solve the above problems, and aims to facilitate the improvement of system performance and realize the expansion of bus functions.

Means for Solving the Problems> The present invention solves the above problems, and the present invention solves the problems described above.
A data transfer mode designation line and a data transfer mode acceptance line are provided in the system bus to which the slave is connected, and the
When starting a data transfer, the master sends an address and displays the transfer mode to be used on the data transfer mode designation line, and the bus slave can respond to the transfer mode specified by the data transfer mode designation line. If so, the data transfer mode acceptance line is driven along with a normal acknowledge response to notify the bus master that it is possible to respond to the transfer mode specified in this cycle, and the bus master receives the acknowledge response. When receiving data, if the bus slave is able to respond to the specified transfer mode based on the state of the data transfer mode acceptance line, it continues to execute this transfer protocol, and if it is not able to respond, it executes it using a primitive transfer protocol. This is a bus control system characterized by continuous data transfer.

<Embodiment> FIG. 1 shows a block diagram of a bus control system in which the present invention is implemented.

In this figure, 1 is a bus master device that supports the protocol related to the present invention, 2 is a bus slave device #1 that supports only one-word data transfer, and 22 is a bus that supports block data transfer and one-word data transfer.・Slave device #2. Master 1, slave #1. #2
is connected to normal bus B, and has an address strobe signal true that specifies the address of the slave to be involved in data transfer, a data strobe signal ■ that requests data transfer, and a data acknowledge signal that notifies the slave that data transfer is complete. Sends and receives signal DTACK.

Furthermore, data transfer mode lines XM,
A data transfer mode acceptance signal mPAcK is provided.

Next, the operation of this bus control system will be explained using the time chart shown in FIG.

First, in cycle ■, master 1 is slave 2+
This is a case where an address is sent to (#1) and one word data transfer mode or block data transfer mode is displayed on the transfer mode designation line XM.
After sending out the strobe signal (2), the slave 21 sends out a data acknowledge signal (1)T]σK, and the data transfer mode acceptance signal -flK remains unchanged.

That is, if the master 1 specifies the one-word data transfer mode for the slave 21, the slave 21 continues the transfer protocol and starts the one-word data transfer operation, and if the block data transfer mode is specified, the slave 21 starts the data transfer operation. Since there is no change in the transfer mode acceptance signal PACK, the master 1 knows that the slave 21 is unable to respond in this mode, and uses a primitive transfer protocol, a one-word data transfer protocol.

Next, in cycle ■, master 1 is connected to slave 22.
(This is a case where the address is sent to #2> and the block data transfer mode is displayed on the transfer mode designation line change.

That is, the master 1 specifies the block data transfer mode to the slave 22, receives the data transfer mode acceptance signal PACK from the slave 22, learns that data can be transferred in this mode, and continues this protocol. .

In this way, specify the data transfer mode from master 1,
The slave side sends a transfer mode acceptance signal to determine whether a response is possible, so the bus functionality is expanded and
It is possible to mix cards that support old and new protocols.

<Effects of the Invention> As described above, according to the bus control system of the present invention, even if there is a mixture of protocols used within the system, the performance of the system can be easily improved without requiring any special changes using software or the like. For example, if a card designed to respond to single-word data transfers exists, and a card with a block data transfer mode is added due to demands for improved system performance. However, you can use the new card together with your existing card.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a bus control system embodying the present invention, and FIG. 2 is a time chart showing the operation of the bus control system of the present invention. 1...Master N 2+ + 22...Slave, B
···bus.

Claims (1)

[Claims] A system in which a bus master and a bus slave are connected
A data transfer mode designation line and a data transfer mode acceptance line are provided on the bus, and the bus master sends an address when starting data transfer and displays the transfer mode to be used on the data transfer mode designation line; If the bus slave can respond to the transfer mode specified by the data transfer mode designation line, it drives the data transfer mode acceptance line with a normal acknowledge response, and instructs the bus master in the transfer mode specified in this cycle. When the bus master receives the acknowledge response, if the bus slave is capable of responding to the specified transfer mode based on the state of the data transfer mode acceptance line, the bus master transfers the transfer mode. A bus control system that continues to execute a protocol, and if a response is not possible, continues data transfer using a primitive transfer protocol.