Instruction Memory testing routine (IMMtst). Performs full test of IMEMn by cpu(n-1).
 The number of the errors, counted by cpu(n) is stored in the location 0xF00n of the DBANK.
 First 63 errors detected by each cpu lead to store the corresponding IMEM address in DBANK,
 according to the following map:
 ; F004-F042 - addresses of IMEM1 with errors
 ; F043-F081 - addresses of IMEM2 with errors
 ; F082-F0C0 - addresses of IMEM3 with errors
 ; F0C1-F0FF - addresses of IMEM0 with errors
 There is additional option in the program.
 If in configuring .tcs file, in I/O space at the address 0x3055 we have 1, the test
 will run otherwise - not.
 This option may be usefull in ROBs, if we want this test running in some chips only.
 When running, the 0x3055 is cleared and next pretrigger will make the chip
 not to start the test. Code, where the program alters 0x3055 from 0 to 1 is now commented.
 Important: The program code in this routine should be the same for all cpus.
 No use of #ifdef cpuX #endif construction. This is, because the program in certain cpu is recovered
 by copying from other one.