摘要:
A system-on-chip including an ingress arbiter module to receive a plurality of service requests from a plurality of devices located upstream to access a resource located downstream. Each of the service requests includes a quality of service value and a first timing budget value specified by the respective device to indicate an amount of time in which the respective service request is to be serviced by the resource. The ingress arbiter module selects a first service request based on the quality of service values, the first timing budget values, and a time delay associated with arbitrating the plurality of service requests and outputting the first service request downstream. A timing budget generator module generates a second timing budget value for the first service request based on the first timing budget value associated with the first service request, and the time delay.
摘要:
The capacity of programmable controllers with a processor module and I/O modules connected in a single equipment rack is expanded by connecting an I/O expansion module in one of the positions normally occupied by a conventional I/O module. The I/O expansion module communicates with the processor module through the rack backplane and also communicates with other racks of I/O modules and with node I/O modules through a serial data channel. Data for I/O modules on the serial data channel are stored in a bulk storage area in the processor module to expand the effective size of an image table of I/O status data that is maintained by the processor module. The processor module is programmed to operate with a backplane controller in the I/O expansion module to transfer data in or out of the bulk storage area. Besides the backplane controller, the I/O expansion module includes a serial channel controller, a common memory and arbitration circuity which allows the controllers to alternate access to the common memory and to exchange data. The serial channel controller controls multiplexing and demultiplexing of I/O status data with the I/O modules through the serial data channel.