JPH06230863A - Daisy chain circuit for bus interface - Google Patents

Abstract

PURPOSE:To automatically control the propagation of a daisy chain signal following a change in the loading of a module without requiring human intervention. CONSTITUTION:Signal pins for indicating the existence of the loading of modules 1, 2 are preveiously allocated to connectors for connecting a back plane 8 to the modules 1, 2. Signal detecting means 3a, 3b for detecting the loading of respective modules 1, 2 and switching means 4a, 4b for switching a daisy chain signal 9 based upon the detection results of the means 3a, 3b are mounted on the back plane 8 in a unit of slots loading the modules 1, 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a daisy chain circuit of a bus interface in a device such as a computer system in which a plurality of modules are connected to a shared bus.

[0002]

2. Description of the Related Art Conventionally, a bus used in a computer system is a VME specified in IEEE 1014.
The (VERSA MODULE EUROPE) bus is known. The daisy chain circuit of this bus interface is shown in FIG.
2 outputs a bus request signal 31 in order to use the bus, and the bus arbitration device 30 receiving this outputs the bus use permission signal 32. The bus grant signal 32 is connected between the modules 1 and 2 by a daisy chain. Therefore, when the bus grant signal 32 is mounted on the common bus, the modules 1 and 2 are packed so that empty slots are not formed. Modules 1 and 2 with empty slots
When it is desired to mount the daisy chain signal, as shown in FIG. 9B, the daisy chain signal may be set to be transmitted downstream by the jumper lines 41a and 41b on the back plane 8. In addition, there is also a dedicated module to keep the daisy chain from breaking for empty slots.

[0003]

In the conventional daisy chain circuit of the bus interface described above, when the module is not mounted, the daisy chain signal is jumpered on the backplane chain in order not to interrupt the daisy chain signal. It is necessary to mount a board (dummy board) just for passing daisy chain signals, and whenever work such as adding or changing a module occurs, change the jumper settings or replace the dummy board every time. Annoying work was occurring. In addition, if the jumper setting is wrong, there is a problem that not only the functional operation as a module cannot be performed but also the entire system performs an abnormal operation.

[0004]

The circuit of the first aspect of the present invention is
In a daisy chain circuit of a bus interface in a device in which a plurality of modules share a bus, with respect to a connector connecting a backplane and each module,
A signal detection unit that pre-allocates a signal indicating whether or not the module is mounted, and detects the state of the signal output from the predetermined signal pin in each slot unit to which the module is connected, A daisy chain circuit characteristic of an interface is characterized in that switching means for performing switching setting of the daisy chain in response to the state of the signal is provided on the backplane.

In the circuit of the second aspect of the present invention, in a daisy chain circuit of a bus interface in a device in which a plurality of modules share a bus, software-controlled daisy chain switching is set for each slot unit to which the modules are connected. A bus interface daisy chain circuit characterized in that switching means is provided on the backplane.

[0006]

According to the first aspect of the present invention, the mounting state of the module can be recognized for each slot in which each module is mounted,
If the module is installed, connect the daisy chain signal from the upstream to the daisy chain receive line of the module in the slot and connect the daisy chain output line from the module to propagate to the downstream module. . On the other hand, when the module is not connected, the switching operation of the daisy chain signal is performed so that the daisy chain signal from the upstream is directly propagated to the downstream.

According to the second aspect of the present invention, the daisy chain signal can be switched to any slot by software control, so that the daisy chain signal can be propagated without interruption of the daisy chain. Becomes

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, which illustrates a first embodiment of the present invention, this embodiment includes two modules 1 on a backplane 8.
And 2 show the system to be implemented. The modules 1 and 2 are, for example, input / output control cards that form a system, and the number of such modules increases or decreases depending on the scale of the system. Modules 1 and 2 on the backplane 8
Corresponding to the signal detecting means 3a, 3b and the switching means 4
a and 4b are provided. Between the backplane 8 and each of the modules 1 and 2, other control signals (not shown) such as a signal 5a indicating the mounting state of the module, a bus grant-in signal 6a, and a bus grant-out signal 7a are exchanged.

FIG. 2 shows a concrete circuit example of the signal detecting means 3a and the switching means 4a of FIG. 1 together with the module 1. The inverter 21, the resistor and the 5V power source in FIG. 2 correspond to the signal detecting means 3a, and the two tri-state drivers 22 and 23 correspond to the switching means 4a.

When the module 1 is mounted on the backplane 8, the experimental state signal 5a is at the low (ground) level, so the tristate driver 23 is enabled, and the daisy chain signal 9 is transmitted via the tristeer 23. And is output to the module 1 as a bus grant-in signal 6a. The output of the other tri-state driver 22 becomes high impedance because the gate of the tri-state driver 22 is closed because the output of the inverter 21 is at high level.

As a result, the bus grant-in signal 6a input to the module 1 becomes the bus grant-out signal 7a and is output downstream. At this time, the state of the variable grant-in signal 6a does not always become the state of the bus grant-out 7a, and if the module 1 is requesting the bus, the signal of the bus grant-out 7a is
It indicates an invalid state.

Next, considering the case where the module 1 is not mounted, since the mounting state signal 5a becomes high level, the output of the inverter 21 becomes low level, the tristate driver 22 is enabled, and the daisy chain signal 9 is generated. Appears at the output of the tri-stearate driver 22 and will be propagated to downstream modules.

FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is a detailed view thereof. 3 and 4
In FIG. 2, the same reference numerals as those in FIGS. 1 and 2 are attached, and other constituent drafts have the same functions.

However, in the first embodiment, the switching means 4a and 4b respond to the mounting state signal 5a to determine whether to output the daisy chain signal from the upstream to the modules 1 and 2 or the downstream. In contrast to the control, in the present embodiment, the switching means 4a and 4b respond to the mounting state signal 5a by daisy chaining either the daisy chain signal from the upstream side or the signal output from the modules 1 and 2 to the downstream side. The difference is that it switches to chain.

FIG. 4 is a detailed view of the signal means 3a and the switching means 4a corresponding to FIG. 2, and the operation thereof is the same as that of FIG.

Referring to FIG. 5, which shows a third embodiment of the present invention, this embodiment shows a system in which a CPU 10 and two modules 1 and 2 are mounted on a backplane 8. C
The PU controls the modules 1 and 2. The backplane 8 includes switching means 4a, 4 corresponding to the modules 1, 2.
b and switching means 4a, 4b according to instructions from the CPU 10.
Selection means 11 is provided for outputting the switching indicating signals 12a and 12b for each of them.

The CPU 10 detects the presence of a module by issuing a predetermined command and obtaining a predetermined response in order to confirm the presence of the modules 1 and 2 connected to the backplane 8 after the system is powered on. The switch instruction signals 12a and 12b are kept at a low level for the confirmed modules, and the switch instruction signals are issued for the slots judged not to have the modules 1 and 2. The signals 12a and 12b are kept at a high level.

FIG. 6 shows a specific circuit of the switching means 4a in FIG. 5 together with the module 1. Here, when the module 1 is mounted, the CPU 10 keeps the switching instruction signal 12a for the module 1 at a low level, and when the module 1 is not mounted, the CPU 10 sets the switching instruction signal 12a for the module 1 to 12a. The selection means 11 is instructed to maintain the high level. Since the operation after this is the same as the operation of the answer shown in FIG. 4, description thereof will be omitted.

FIG. 7 is a fourth embodiment of the present invention, and FIG. 8 is a fourth embodiment.
The detailed drawing of the principal part of the Example of FIG. In the present embodiment, the switching means 4a, 4b causes the switching instruction signal 12a,
The third embodiment is similar to the third embodiment in that the switching operation is performed in response to 12b, and the first embodiment is that it controls whether the daisy chain signal from the upstream side is output to the modules 1 and 2 or the downstream side. Common with the example. Therefore, the detailed reply operation shown in FIG. 8 is similar to the detailed reply operation shown in FIG.

[0020]

As described above, according to the present invention, even if the module is faced when the system configuration is changed, the daisy chain signal can be automatically propagated correctly to the downstream side. It has the effect of being unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a signal detecting means and a switching means shown in FIG.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a signal detecting means and a switching means shown in FIG.

FIG. 5 is a block diagram of a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a switching unit shown in FIG.

FIG. 7 is a block diagram of a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram of the switching means shown in FIG.

FIG. 9 is a diagram showing a conventional example.

[Explanation of Reference Signs] 1, 2 Modules 3a, 3b Signal detecting means 4a, 4b Switching means 5a, 5b Mounting state signal 6a, 6b Bus grant in signal 7a, 7b Bus grant out signal 8 Backplane 9 Daisy chain signal 10 CPU 11 Selection means 12a, 12b Switching instruction signal 21 Inverter 22, 23 Tri-state driver 30 Bus arbitration device 31 Bus request signal 32 Bus use permission signal 41a, 41b Jumper wire

Claims (6)

[Claims] 1. In a daisy chain circuit of a bus interface in a device in which a plurality of modules share a bus, a signal for indicating whether or not a module is mounted is provided in advance with a pin for a connector connecting a backplane and each module. For each slot to which the module is connected, signal detection means for detecting the state of the signal output from the predetermined signal pin, and daisy chain switching setting in response to the state of the signal are set. A daisy chain circuit of an interface, characterized in that switching means for performing the switching is provided on the back plane. 2. The daisy chain circuit of the bus interface according to claim 1, wherein the switching setting is performed by outputting a daisy chain signal from an upstream side to a module or a downstream side. 3. The daisy chain of the bus interface according to claim 1, wherein the switching setting is performed depending on which of the daisy chain signal from the upstream side and the signal output from the module is daisy chained to the downstream side. circuit. 4. In a daisy chain circuit of a bus interface in an apparatus in which a plurality of modules share a bus, a switching means for performing daisy chain switching setting by software control is provided for each slot to which the modules are connected on the backplane. Bus interface daisy chain circuit, which is provided in the. 5. The daisy chain of the bus interface according to claim 4, wherein the switching setting is performed by daisy chaining either a daisy chain signal from an upstream side or a signal output from the module to a downstream side. Chain circuit. 6. The daisy chain of a bus interface according to claim 4, wherein the switching setting is performed depending on whether the daisy chain signal from the upstream side or the signal output from the module is daisy chained to the downstream side. circuit.