Method of operating a buffer memory to provide a trigger pattern by storing a trigger code in preselected areas of the buffer memory

A method of operating a buffer memory that has a multiplicity of memory locations in an address space having a first dimension and a second dimension, each memory location storing a numerical value, said method comprising the steps of:

• (a) loading the memory locations within a selected area of the address space with a trigger code,
• (b) acquiring a succession of pairs of data words from an input signal, each pair being composed of a first data word and a second data word, the range of the first data word being equal to at least the range of the first dimension of the address space and the range of the second data word being equal to at least the range of the second dimension of the address space,
• (c) for each pair of data words,
• (i) reading from the buffer memory the numerical value stored at the memory location whose address in the first dimension of the address space is defined by a first address word and whose address in the second dimension of the address space is defined by a second address word, the first and second address words being related in a predetermined fashion to the first and second data words,
• (ii) comparing said numerical value with said trigger code,
• (iii) generating a predetermined response signal when said numerical value bears a predetermined relationship to said trigger code, and
• (iv) incrementing said numerical value by a predetermined amount and writing the incremented numerical value to the memory location that was read in step (c)(i) when said numerical value does not bear the predetermined relationship to said trigger code,
• (d) subsequently generating the first and second address words independently of the first and second data words, and
• (e) for the first and second address words
• (i) reading from the buffer memory the numerical value stored at the memory location defined by the first and second address words,
• (ii) writing the numerical value unchanged back to the memory location read in step (e)(i) when said numerical value bears the predetermined relationship to said trigger code, and
• (iii) decrementing the numerical value by a selected amount and writing the decremented numerical value back to the memory location read in step (e)(i) when said numerical value does not bear the predetermined relationship to said trigger code.

Buffer memory apparatus for generating a trigger when a waveform in the form of pairs of data words falls outside a defined region comprising:

• a multiplicity of memory locations occupying a two-dimensional address space and each storing a numerical value,
• means for defining an area of the address space corresponding to the defined region and loading the memory locations within the defined area each with a trigger code,
• means for receiving the pairs of data words, each pair having a first data word and a second data word,
• means responsive to each pair of data words from the receiving means for reading from the buffer memory the numerical value stored at the memory location whose address is defined by a first address word and a second address word related in a predetermined fashion to the first and second data words, comparing the numerical value read from the buffer memory with said trigger code, and generating the trigger when said numerical value bears a predetermined relationship to said trigger code.