Active termination in a multidrop memory system
AssigneeMicron Technology, Inc.
InventorsRoy Greeff, Terry R. Lee, Ron Harrison
Life of this patent
Estimating the term…
Abstract
An active termination circuit is incorporated into the devices connected to a multidrop bus. By including the active termination circuit on the devices instead of the bus, termination resistors can be removed from the system PCB, which saves costs and frees up precious space on the PCB. The active termination circuit has a termination enabled state and a termination disabled state. The active termination circuit is selectively placed into the enabled or disabled states in specified devices depending upon, for example, device location or communication traffic on the bus. The multidrop system can also utilize a separate passive termination mechanism in combination with the active termination circuits utilized in the devices.
Claims50
A multidrop memory system comprising:
- a transmission line;
- and
- a plurality of memory devices connected to said transmission line, at least one of said memory devices comprising a termination circuit for selectively enabling and disabling termination of said transmission line,
- wherein said at least one memory device enables and disables the termination of said transmission line based on communication traffic on said transmission line and the termination circuit is adjustable such that when it is enabled it substantially optimizes termination of said transmission line for different loading in said system.
A memory system comprising:
- a muitidrop bus;
- a memory controller, said memory controller comprising a first termination circuit coupled to said bus for selectively enabling and disabling termination of said bus;
- and
- a plurality of memory devices connected to said bus, at least one of said memory devices comprising a second termination circuit for selectively enabling and disabling termination of said bus,
- wherein said controller uses said first termination circuit to enable and disable the termination of said bus based on a direction of information on said bus, said at least one memory device uses said second termination circuit to enable and disable the termination of said bus based on information traffic on said bus and each termination circuit is adjustable such that when it is enabled it substantially optimizes termination of said bus for different loading in said system.
A processor system comprising:
- a processor;
- a plurality of memory devices coupled to said processor via a transmission line;
- and
- a passive termination element coupled to a first end of the transmission line,
- wherein said processor comprises means for selectively enabling and disabling termination to the transmission line and said means is adjustable such that when termination is enabled said means substantially optimizes termination of said transmission line for different loading in said system.
A method of operating a multidrop memory system having a plurality of memory devices connected to a transmission line, said method comprises the steps of:
- providing each memory device with a termination circuit coupled to the transmission line;
- calibrating each termination circuit so that when enabled each termination circuit provides substantially optimal termination to the transmission line;
- determining for each memory device whether termination of the transmission line is required;
- and
- controlling each termination circuit to enable termination of the transmission line if it is determined that termination is required and to disable termination of the transmission line if it is determined that termination is not required,
- wherein said determination step is performed based on at least one of a location of the memory device along the transmission line and a direction of information traffic on said line.
A method of operating a multidrop memory system having a controller coupled to a first end of a bus and a plurality of devices connected between the first end and a second end of the bus, said method comprising the steps of:
- providing the controller with a termination circuit coupled to the bus;
- calibrating the termination circuit so that when it is enabled the termination circuit provides substantialy optimal termination to the bus;
- providing a passive termination element at the second end of the bus;
- determining whether termination of the bus is required;
- and
- controlling the termination circuit to enable termination of the bus if it is determined that termination is required.
Dependencies are inferred from the claim text.