Browse Prior Art Database

MEMORY MANAGEMENT FOR TOKEN-BUS LAN

IP.com Disclosure Number: IPCOM000005601D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-18
Document File: 4 page(s) / 134K

Publishing Venue

Motorola

Related People

Orly Kremien: AUTHOR [+2]

Abstract

To support the IEEE 802.4 message priorities, the Token Bus Controller(TBC) chip uses a powerful, flexi- ble memory and buffer management structure and maintains four transmit queues and four receive queues. The RAM based structures that the TBC uses for buffer management include: Frame Descriptors (FD) List(s) - contain a linked list of frame descriptors. Separate lists of FD's are maintained for a free FD pool, four receive queues, and four transmit queues. A frame descriptor con- sists of frame attributes (source address, destination address, size, etc.), a pointer to the associated BD list and a pointer to the next FD in the queue.

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MOTOROLA Technical Developments Volume 6 October 1986

MEMORY MANAGEMENT FOR TOKEN-BUS LAN

by Orly Kremien, Yehuda Shvager

   To support the IEEE 802.4 message priorities, the Token Bus Controller(TBC) chip uses a powerful, flexi- ble memory and buffer management structure and maintains four transmit queues and four receive queues. The RAM based structures that the TBC uses for buffer management include:

Frame Descriptors (FD) List(s) - contain a linked list of frame descriptors. Separate lists of FD's are maintained for a free FD pool, four receive queues, and four transmit queues. A frame descriptor con- sists of frame attributes (source address, destination address, size, etc.), a pointer to the associated BD list and a pointer to the next FD in the queue.

Buffer Descriptors (BD) List(s) - contain a linked list of buffer descriptors. These BD's may belong to the free pool or may be associated with an FD in either a transmit or receive queue. A buffer descrip- tor consists of buffer attributes, a pointer to its data buffer and a pointer to the next BD in the list.

Data Buffers - adata buffer is linked to each buffer descriptor in the free buffer pool and to BD's that are associated with FD's in the receive or transmit queue. the data buffer contains the actual data.

A message frame is comprised of a frame descriptor, a buffer descriptor list and associated data buffers (see figure 1).

   During transmission, the host processor creates frame descriptors, buffer descriptors and data buffers and links the frame descriptors to the appropriate priority transmit queue. During reception, the TBC uses frame descriptors and buffer descriptors from the free FD and free BD pools (see figures 2 and 3). Received messages are assigned to the proper receive queue. The host processor removes the frame from the receive queue as it desires.

   A key feature of the TBC memory management is its ability to allocate buffers dynamically to the appropriate queue upon demand. The host does not have to allocate frame and buffer descriptors for each queue in ad- vance. Instead, the host prepares one pool of free frame descriptors and one pool of free buffer descriptors and these two serve all queues. The TBC dynamically allocates FD and BD's to the appropriate queue...