What are S & SPS in Timing chart after acceptance of interrupt request?

"S" is the stack pointer.
"SPS" is the page selected by the stack page selection bit of the CPU mode register.
"Waiting time for post-processing of pipeline" is the internal CPU processing time for the preceding instruction. When instructions are executed continuously, this processing is executed simultaneously with the first two cycles of the next instruction so no wait time is generated. However, wait time is generated when an interrupt occurs.
Although the expression "pipeline" is used, there is no queue buffer, etc. in the 740 Family. (#104768)