Channel ready.
When an ISA expansion board requires more wait states than would normally be supplied by the default ready timer on the system board, it should deassert CHRDY when its address decoder recognizes an address and the appropriate command line (SMRDC#,SMWTC#,MRDC#,etc.).
This prevents the default ready timer on the system board from timing out and issuing READY# to the microprocessor until CHRDY is asserted again by the currently-addressed ISA device. As long as the currently-addressed ISA card holds CHRDY deasserted, the microprocessor's READY# input is kept deasserted, causing wait states to be inserted in the bus cycle.
When the currently-addressed device is ready to end the bus cycle, it allow CHRDY to become asserted again (CHRDY has a pull-up resistor on the system board),enabling the default ready timer to assert the microprocessor's READY# input.
When the microprocessor samples its READY# input asserted at the end od the current data time, it ends the bus cycle.