Enhancement of input/output for non source-synchronous interfaces

Abstract

An interface for use of device whose core circuitry operates in one voltage domain, but exchanges signal with another device (or ''host'') according a different voltage domain, and the use of such an interface for supplying data using a double data rate (DDR) transfer, is presented. One concrete example of this situation is a memory card, where the internal circuitry uses one voltage range for its core operating voltages, but exchanges signals with a host using different, input / output voltage range. According to a general set of aspects, the interface receives data signals from the device at the device's core operating voltage domain, individually level shifts these to the input / output voltage domain, and then combines them into a DDR signal for transfer to the host device, where a (non-level shifted) clock signal from the host device is used as the select signal to form the DDR data signal.

Description

technical field [0001] The present invention relates generally to the field of electrical interfaces and, more particularly, to the data output of non-source synchronous interfaces. Background technique [0002] A simple interface for data transfer purposes between integrated circuit devices will typically include a clock signal provided by a host device that is used by a slave device to output data to the host. A specific example is a host read cycle to a memory card or other storage device. The timing of data output from the slave device then depends on the arrival of the clock signal. There is an ongoing process for increasing the performance of these devices. When higher transfer speeds are desired, one approach is to migrate the interface protocol to a source synchronous scheme where both clock and data signals are provided from the same device, such as in the DDR (Double Data Rate) arrangement used in DRAM devices . However, this approach may not be practical to us...

AI Technical Summary

Problems solved by technology

However, this method may not be practical to use in many devices as it may result in substantial changes to the interface (e.g. adding signal pins)

Thus, there is room for improvement in such interfaces

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