Trap Mode Instructions - IBM 7090 Instruction-Reference

Transfer on Data Channel Redundancy Check
TRC ± XXXX(I, L) Figure 5. 3-32
If the data channel redundancy check trigger is on, a transfer is taken to location X
and the trigger is turned off. If the trigger is off, the computer takes the next sequential
instruction. Operation codes +0022, -0022, +0024, -0024, +0026, -0026, +0027, and
-0027 are used to select data channels A through H, respectively.
Transfer on Data Channel End of'File TEF ±XXXX(I, L) Figure 5.3-32
If the data channel end-of-file trigger is on, a transfer is taken to storage location
X and the trigger is turned off. If the trigger is off, the computer takes the next in-
struction in sequence. Operation codes +0030, -0030, +0031, -0031, +0032, -0032,
+0033, and -0033 are used to select data channels A through H, respectively.
5.3.06 Trap Mode Instructions
The 7090 can be operated in either of two modes, normal or trapping. Entrance to
trapping mode is gained by executing the ETM instruction. Exit is accomplished by
using the LTM instruction or the clear or reset keys on the console. Trapping mode
affects the operation of transfer instructions except TTR. In trapping mode, the location
of each transfer instruction is stored in the address portion of location 0000. Successful
transfers are not executed; instead, an instruction transfer, or trap, is taken to location
0001. One instruction, trap transfer, is immune to trapping mode. The locating of
successful transfers and the trap to a common check point make trapping mode useful
for debugging program flow. Unsuccessful transfers have their location stored in the
address portion of 0000, but do not trap to 0001.
Enter Trapping Mode
ETM +0760 ... 0007 (I, L)
This instruction places the computer in trapping mode by turning on the trap mode
trigger on Systems 2.10.53.1. The computer remains in trapping mode until a LTM
instruction is executed or the clear or reset buttons are depressed. ETM is a primary
operation 76 instruction and requires an I and an L cycle.
TRA in Trapping Mode
TRA +0020 (I, E)
The effect of trapping mode on a transfer is shown in Figure 5.3-33.
Leave Trapping Mode
LTM -0760 ... 0007 (I, L)
This instruction returns the computer to normal mode by turning off the trap mode
trigger on Systems 2.10.53.1. This is a primary operation 76 instruction, and an I
and an L cycle are required.
Trap Transfer
TTR +0021 (I)
This is the only instruction which provides an instruction transfer to location X
regardless of the operating mode of the computer. The TTR instruction nullifies the
transfer blocking circuits of trapping mode (Systems 2. 10.53. 1) and operates like TRA.
Store Location and Trap
STR -1000 (I, E) Figure 5.3-34
This instruction stores its location plus one in the address portion of storage loca-
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