Signalling protocol for signalling start of reset processing in serial ATA bus protocol

A method for use on any serial bus wherein normal operation including normal operation during sleep mode requires constant transmission of data or fill characters so that receivers coupled to said bus do not lose clock synchronization, for initiating predetermined processing to make sure that the bus is operating properly, comprising:

• detecting occurrence of a master reset signal and responding thereto by transmitting on a serial bus a predetermined signal to indicate a need to commence predetermined processing to make sure said serial bus is operating correctly, said predetermined signal comprising at least one silent interval of a predetermined duration known to all transceivers coupled to said serial bus, each said silent interval ended by a burst of any data of any length, said predetermined signal comprising the transmission of said one or more silent intervals of predetermined duration(s) which are known to all transceivers coupled to said serial bus, said silent interval(s) transmitted in a predetermined pattern which also is known to all transceivers coupled to said serial bus;
• sending a long silent interval at the end of said predetermined signal to indicate cessation of transmission of said predetermined signal, said long silent interval having a predetermined duration known to all transceivers coupled to said bus and different from the duration of any silent interval in said predetermined signal and hereafter referred to as the “over” signal;
• detecting in each other transceiver coupled to said bus said silent interval(s) and measuring the duration of each one, and if said duration of said silent interval or the durations and pattern of durations of said silent intervals matches the known pattern(s) defining said predetermined signal, sending a signal to a reset software process to cause said reset software process to perform said predetermined processing;
• upon detection of said “over” signal, transmitting a predetermined handshaking signal back to said transceiver which sent said predetermined signal, said handshaking signal being known to all transceivers coupled to said bus.

A low power receiver apparatus for monitoring a serial data bus for the transmission of a unique signal pattern which indicates a need to perform reset processing to re-establish communications on said serial data bus, comprising:

• a squelch detector having one or more inputs coupled to the receive lines of said serial bus and having an output line which is driven to a first state during silent intervals on said bus and which reverts to a second state whenever anything other than silence is being transmitted on said bus;
• a timer having an enable count input coupled to said output line of said squelch detector and having either an internal clock driving a counter or a clock input for driving said counter, and having a data output at which the count of said counter appears, said timer functioning to count clock cycles only during silent intervals on said bus;
• and
• a signal pattern detector having an input coupled to said output signal line and having a data input coupled to said data output of said timer, and functioning to calculate the duration of the one or more silent intervals on said bus that comprise said unique signal pattern and compare the durations of said one or more silent intervals to stored data defining how long these durations are in said unique signal pattern and the order, if any, in which the silent intervals of predetermined durations occur if said unique signal pattern is comprised of more than one silent interval of different durations, and for activating an output signal when said unique signal pattern is detected.