Transition reduction encoder using current and last bit sets

Details Transition reduction encoder using current and last bit sets Transition reduction encoder using current and last bit sets

2000-12-28

2003-03-25

Williams, Howard L. (Department: 2819)

Coded data generation or conversion

Digital code to digital code converters

To or from minimum d.c. level codes

C341S055000

Reexamination Certificate

active

06538584

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to circuits and, more particularly, to sending encoded bits over interconnects.
2. Background Art
Interconnects are used to transmit signals (such as bits) over relatively long distances either inside an integrated circuit (also called a chip) and between integrated circuits.
FIG. 1
illustrates a system
10
of integrated circuits including integrated circuits IC
0
, IC
1
, IC
2
. . . ICn. The integrated circuits are connected through a bus
14
. Integrated circuit IC
0
could be a controller for the other integrated circuits or could be the same as other integrated circuits. System
10
may be a system that is referred to as multi-drop system in which one or more of integrated circuits IC
1
, IC
2
. . . ICn are selectively joined to bus
14
. System
10
, however, is not limited to a multi-drop arrangement. System
10
may be a memory system in which IC
0
is a memory controller (either joined with a processor on chip or in a different chip from the processor) and in which integrated circuits IC
1
, IC
2
. . . ICn are, for example, dynamic random access memory (DRAM) chips that are on one or more PCBs. System
10
could also involve a multi-processor system.
Address, data, and control bits on bus
14
may be on separate conductors of bus
14
or they may be, for example, time division multiplexed or packetized. For example, bus
14
may include some conductors used to carry only address bits, some conductors used only to carry only control bits, and some conductors used to carry only data bits. Or, some conductors may be used to transmit some combination of address, control, and/or data bits at different times or through a packetized or arrangement.
FIG. 2
illustrates a system
20
including integrated circuits IC
0
, IC
1
, IC
2
. . . ICn. The integrated circuits are connected through busses
24
-
1
,
24
-
2
, . . .
24
-n and an optional conductor
28
. Note that IC
0
may be a controller of the other integrated circuits or could be the same as other integrated circuits. System
20
is of the type that is sometimes referred to as point-to-point bus system. System
10
, by contrast, is referred to as a radial bus system.
Bidirectional signaling refers to using the same conductors to transmit signals in both directions. For example, data may be transmitted either to or from an integrated circuit. If the same conductor is used in both directions, the signaling is bi-directional. The bi-directional signaling may be sequential or simultaneous. In the case of sequential bi-directional signaling, enable signals may be used to, for example, tri-state or turnoff unused drivers or receivers. In the case of simultaneous bi-directional signaling, the threshold voltage of the receiver may be changed depending on the state of the adjacent driver. For example, if the adjacent driver is transmitting a 0, the receiver threshold may be set to Vcc/4. If the remote driver is also 0, the threshold will not be met. If the remote driver is a 1, the Vcc/4 threshold will be met. If the adjacent driver is transmitting a 1, the receiver threshold may be set to 3 Vcc/4. If the remote driver transmits a 1, the threshold will be met and if it transmits a 0, the threshold will not be met.


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