JP2990192B1 - SCSI control circuit - Google Patents

Abstract

Kind Code: A1 When a SCSI device continues to acquire a bus and a hang-up occurs, only a hung SCSI device is selectively reset, and another SCSI device is reset.
Provide a SCSI control circuit that prevents the SI device from resetting. When an enable signal for driving a busy (BSY) signal issued by the SCSI device is active, or when a busy signal on the SCSI bus is inactive, a reset (RS) on the SCSI bus is performed.
T) means for controlling to accept the signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit device for controlling a device connected to a bus, and more particularly, to a SCSI (Smaller) device.
The present invention relates to a control circuit for a device (referred to as a “SCSI device”) connected to a Computer Systems Interface (bus).

[0002]

2. Description of the Related Art A conventional SCSI bus will be described below. If a predetermined time has elapsed while the BSY (busy) signal on the SCSI bus remains active, the host computer determines that the SCSI bus has hung up,
By activating the RST (reset) signal on the I bus, a SCSI reset is executed, and all the SCSI devices on the SCSI bus execute their own reset processing.

Here, the BSY signal of the SCSI bus is used to inform another device (apparatus) that the initiator and the target are connected on the SCSI bus and are using the bus. The BSY signal is driven by the target device. In addition, besides this, for example, in the arbitration phase for competing for the right to use the bus, the BSY signal is asserted by a device requesting the right to use the bus.

The RST signal can be transmitted from all devices on the SCSI bus,
In the case of a hard reset, the device that detects the ST signal forcibly releases use of the bus and returns to the initial state.

[0005]

As described above, the conventional S
In the CSI bus control method, when a hang-up occurs in a certain SCSI device, not only the hung-up SCSI device but also the non-hung-up SCSI device executes the reset process.

For this reason, the SCS which has not hung up
The SCSI command already issued to the I-device will be interrupted in the middle of processing,
It was necessary to reissue the I command, which was inefficient.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and has as its object to hang up when a SCSI device continues to acquire a bus and hangs up. S that selectively resets only the existing SCSI devices and avoids resetting even SCSI devices that are not hung up
An object of the present invention is to provide a CSI control circuit.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a control circuit for a device connected to a SCSI bus, wherein an enable signal for driving a busy (BSY) signal is active, or Means for controlling to accept the RST signal on the SCSI bus when the busy signal is not active.

[0009]

Embodiments of the present invention will be described. The present invention provides, in its preferred embodiment, S
At least one of an enable signal, which is a control signal for permitting a device connected to the CSI bus to output a driver circuit for driving a busy (BSY) signal, and a signal obtained by inverting a busy signal on the SCSI bus, are active. Sometimes, the reset (RST) signal on the SCSI bus is received and transmitted to the reset terminal of the SCSI controller, and both the enable signal and the busy (BSY) signal on the SCSI bus are inactive (inactive).
In the case of (1), there is provided means for controlling so as to mask the reset (RST) signal.

[0010] The present invention is based on the assumption that when a SCSI device remains in the state of acquiring a bus as a target,
A circuit that receives the RST signal only when the device itself drives the BSY signal or when the BSY signal on the SCSI bus is disabled, utilizing the fact that the SY signal is being driven. When the output of this circuit becomes active, the input RST signal is transmitted by the SCSI controller,
It allows you to reset your device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a system configuration for explaining an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a SCSI device according to one embodiment of the present invention.

Referring to FIG. 1, a host computer 1
And SCSI device 2 (# 1), SCSI device 2
(# 2) and SCSI device 2 (# 3)
It is connected to the bus 3.

Referring to FIG. 2, SCSI device 2
Are a SCSI controller 4, a receiver circuit 51 and a driver circuit 52 for the BSY signal 5, and a driver circuit 52.
And a reset condition determination circuit 7 for determining the condition of the RST signal 6. Note that the reset condition determination circuit 7 corresponds to the SCSI device 2 shown in FIG.
(# 1 to # 3).

The reset condition determination circuit 7 outputs the BSY signal 5
(Inverter) 71 having the input as an input, a logical sum (OR) circuit 72 having the output of the negative circuit 71 and the enable signal 53 as inputs, and the output of the logical sum circuit 72 and the RST signal 6 as inputs. A logical product (AND) circuit 73.

The operation of one embodiment of the present invention will be described. When the SCSI bus 3 is hung up, the hung SCSI device is
Since the SY signal 5 remains driven, the BSY signal 5 on the SCSI bus 3 is active.

For example, when the SCSI device 2 (# 1) hangs up, the BS of the SCSI device 2 (# 1)
The driver circuit 52 for the Y signal 5 is enabled, and the BSY signal 5 on the SCSI bus 3 is active.

On the other hand, if the BSY signal 5 on the SCSI bus 3 is not active, it can be determined that no SCSI device hung on the SCSI bus 3 exists.

When a predetermined time has elapsed while the BSY signal 5 on the SCSI bus 3 remains active, the host computer 1
Determines that SCSI bus 3 has hung up,
The RST signal 6 on the SCSI bus 3 is set to the active state, and the SCSI reset is executed.

It should be noted that the RST signal 6 is asserted to
Opportunities for executing the I reset include a time when the SCSI bus 3 hangs up, a time when the system is started, a time when the system is reset, and the like.
CSI bus 3 is not hung up, that is, SC
The BSY signal 5 on the SI bus 3 is in an inactive state. For this reason, the condition that the BSY signal 5 on the SCSI bus 3 is inactive corresponds to the condition that the RST signal 6 on the SCSI bus 3 is received, and the reset processing of the own device is executed.

The signals input to the reset condition determination circuit 7 incorporated in the SCSI device 2 include an enable signal 53 of the driver circuit 52 of the BSY signal from the SCSI controller 4, a BSY signal 5 on the SCSI bus 3, and S
RST signal 6 on the CSI bus, the output of which is SC
It is connected to the RST terminal to the SI controller 4.
A known controller is used as the SCSI controller 4. When the RST terminal becomes active, the use of the bus is released, the enable signal 53 is made inactive, the output of the BSY signal is stopped, and the initialization is executed. .

The reset condition judging circuit 7 outputs the output of the NOT circuit 71 of the BSY signal 5 on the SCSI bus 3 and the SCSI
The output of the OR circuit 72 with the enable signal 53 of the driver circuit 52 to which the BSY signal from the controller 4 is input is taken.
The output of the AND circuit 73 with the ST signal 6 is connected to the RST terminal of the SCSI controller 4 as an RST signal, and the SCSI controller 4 drives the BSY signal (that is, the enable signal 53 is active), or The RST signal 6 on the SCSI bus 3 is received only when the BSY signal 5 on the SCSI bus 3 is inactive (the output of the NOT circuit 71 is active).

When the SCSI device 2 (# 1) hangs up and the SCSI bus 3 hangs up,
The host computer 1 activates the RST signal 6 on the SCSI bus 3 to execute a SCSI reset.

At this time, since only the SCSI device 2 (# 1) drives the BSY signal 5 on the SCSI bus 3, the SCSI controller 4 of the reset condition determination circuit 7 of the SCSI device 2 (# 1) Is driven, the RST signal 6 is received, and reset processing of the own device is executed.

Other SCSI devices 2 (# 2),
In (# 3), since the BSY signal is not driven, the condition that the SCSI controller 4 of the reset condition determination circuit 7 incorporated therein drives the BSY signal, and the BSY signal 5 on the SCSI bus 3 is Both conditions of inactivity are not satisfied, and the AND circuit 73
, The RST signal 6 is masked, and the received RST signal is not transmitted to the RST terminal of the SCSI controller 4, so that the reset processing is not executed.

When the host computer 1 executes a SCSI reset (asserts the RST signal) when the SCSI bus 3 is not hung up,
Since the SI device does not drive the BSY signal,
Reset condition judgment circuit 7 built in all SCSI devices
The RST signal 6 is received when the BSY signal 5 on the SCSI bus 3 is not active, and the reset processing of the own device is executed.

In the embodiment shown in FIG.
The number of SCSI devices 2 connected to the SI bus 3 is 3
However, it is needless to say that the present invention is not limited to such a configuration. That is, referring to FIG. 3, the host computer 1, the SCSI device 2 (# 1),
SCSI device 2 (# 2), and similarly a total of n SCSI devices up to SCSI device 2 (#n)
It is connected to the I bus, and n is a maximum of 7 in the case of the NARROW-SCSI standard and a maximum of 15 in the case of the WIDE-SCSI standard.

[0027]

As described above, according to the present invention,
The reset process can be executed only for the hung up SCSI device, and the SCSI command issued to the other hung up SCSI device can continue the process as it is. Removes unnecessary reset processing,
This has the effect of improving system performance and bus use efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a SCSI device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a modification of the system configuration according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Host computer 2 SCSI device 3 SCSI bus 4 SCSI controller 5 BSY signal 6 RST signal 51 Receiver circuit 52 Driver circuit 53 Enable signal 7 Reset condition judgment circuit 71 Negation circuit (inversion circuit) 72 OR circuit 73 AND circuit

Claims (3)

(57) [Claims] 1. A control circuit for a SCSI device connected to a SCSI bus, comprising: a device for driving and outputting a busy (BSY) signal;
Alternatively, there is provided means for controlling so as to accept a reset (RST) signal on the SCSI bus and reset the own device when a busy (BSY) signal on the SCSI bus is in an inactive state. SCSI control circuit. 2. An SCSI device connected to a SCSI bus, comprising: an enable signal which is a control signal for permitting an output of a driver circuit for driving a busy (BSY) signal;
A busy (BSY) signal on the I bus, and when at least one of these signals is active, accepts a reset (RST) signal on the SCSI bus and transmits it to the reset terminal of the SCSI controller. And a means for controlling masking of acceptance of the reset (RST) signal when both the enable signal and the busy (BSY) signal on the SCSI bus are inactive. . 3. A SCSI comprising one or a plurality of SCSI devices and a host computer connected to a SCSI bus.
In the bus system, the SCSI device includes an enable signal for driving a busy (BSY) signal, and a busy (BS) signal on the SCSI bus.
Y) and inputting a reset (RST) signal on the SCSI bus when the enable signal is active or the busy signal on the SCSI bus is inactive. Means for driving a busy (BSY) signal when the host computer detecting the hang-up state asserts a reset (RST) signal on the SCSI bus.
S is characterized in that only the SI device executes the reset process and the reset of other SCSI devices is suppressed.
CSI bus system.