CM1K Hardware User’s Manual
45
pattern will execute the RDIST instruction in 1 cycle, when a neuron which recognizes the pattern (i.e. fires) will
participate to the Search and Sort race for up to 16 clock cycles. The Ready line of the chip indicates when all the
neurons have finished the execution of an instruction and can receive a new one.
Write LCOMP (0x02), Read DIST (0x03), Read and Write CAT (0x04) are "snooping" commands meaning they are
making open collector bus mixing. The release of the DATA lines as well as the ID_ and UNC_ lines after the fall of
the DS signal is critical so they can snoop properly.
7.1.2
Multiple read/write to the COMP register
Broadcasting a vector to the neurons is a succession of Write COMP (up to 255 times) ended with a Write LCOMP.
The series of Write COMP can be executed with a sustained DS signal provided that the data is updated and stable
at each new positive edge of the system clock. For reference, the waveforms shown under the paragraph
“Recognizing a vector received through the digital video bus” illustrate the use of a sustained DS signal during the
feed of all but the last component value.
7.2
Typical Timings Constraints
In the example below, a vector of 8 components is learned and then recognized. The resolution of the diagrams
does not allow reading the DATA values of the components and the category, but this is not important for
understanding the timing constraints of the chip.
The DS, RW_, REG and DATA signals are updated at the negative edge of the system clock (G_CLK) so that they are
stable when the neurons read them at the next positive edge of G_CLK. The RDY signal is then immediately pulled
down by the neurons and released at the first positive edge of G_CLK following the completion of the command.
The duration during which the RDY signal is low represents the execution time of the command.
In the case of a Read command, the output DATA is ready to be read when RDY rises.
7.2.1
Learn a vector
The sequence of instructions consists of 7 Write COMP, 1 Write LCOMP, and 1 Write CAT.
When REG is equal to 01, each DS pulse triggers a Write COMP lasting one cycle of G_CLK. The RDY signal has the
same duration as the DS only shifted by one half clock cycle.
When REG is equal to 02, the DS pulse triggers a Write LCOMP. The RDY signal is pulled down for 3 cycles. The fact
that both lines ID_l and UNC_l are pulled up indicates that the input vector is not recognized by any existing
neuron. The subsequent Write CAT command will necessarily commit a new neuron.