Card to Card Communication
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-07
Andrews, L: AUTHOR [+7]
In the system environment of Fig. 1, host processor 1 exchanges data with devices through a device attachment card 2 and a device attachment interface 3 The interface can be symmetrically configured, as shown below to support host-to-host communications as well as host to device exchanges. Card 2 contains a microprocessor for directing its operations.
Card to Card Communication
In the system environment of Fig. 1, host processor 1 exchanges data with devices through a device attachment card 2 and a device attachment interface 3 The interface can be symmetrically configured, as shown below to support host- to-host communications as well as host to device exchanges. Card 2 contains a microprocessor for directing its operations.
The host processor (including the standard complements of CPU, main storage and I/O channel circuits) may be topologically packaged on a plurality of JSI circuit cards. These cards, together with the attachment card 2, may be housed and co-powered in a common frame.
As seen in Fig. 2, the interface 3 connects to a bus containing a multi-line bidirectional data section 11, several lines of unidirectional control section 12 and a two-line "handshake" control section 13. The control section 12 includes four lines for sending control signals to the device and four lines for receiving control/status signals from the device. The control lines 12 directed to the device include a "select" line which is active (-) throughout the period of communication with the device, a "write" line which is active (-) if the operation being conducted is a write output transfer of information to the device via the data bus and inactive (+) if the operation is a "read" data transfer from the device, a last transfer line which is active (-) when a last byte or word of data is being transferred, and a reset line which is pulsed active (+) for establishing a reset condition at the device. The control lines directed to the attachment card include "attention" and "OP end" interrupt lines, for posting specific interruption requests (to the attachment card and/or the host system), a "status" line for posting a specific device status condition, and a "ready" line for indicating attachment card readiness to send or receive data.
The handshaking control lines 13 include a "request" line directed to the attachment card, for indicating device readiness for sending or receiving data, and an "acknowledge" line for indicating attachment card responsiveness to a request.
An ancillary application for the foregoing interface is to sustain attachment of peer host systems, as suggested in Fig. 3. This function may be accomplished by crossconnecting the lines shown in Fig. 2 in the configuration illustrated in Fig. 4.
In this configuration, the select and attention interrupt lines of system A are respectively cross-coupled to the attention interrupt and select lines of system B; the write and device status lines of system A are cross-coupled to the device status and write lines of system B; the last transfer and OP end interrupt lines of system A are cross-coupled to the OP end interrupt and last transfer lines of system B; the reset and ready lines of system A are cross-coupled...