Manual Control Keys - IBM 7090 Instruction-Reference

Entry Keys
There are 36 entry keys on the operator's panel: S, 1-35. Depressing a key sets a
1 in that position; leaving a key normal sets a 0 in that position. Information set in the
entry keys may be entered into storage, executed, or used for a storage inquiry address.
The entry keys may all be reset to 0 by depressing the reset key to the right of position
35.
6. 1. 03 Manual Control Keys
When any manual control key is pressed, a series of single-shots and triggers are
set. Separating the key from the usable signal prevents false indications from noise
generated by the key (Figure 6.1-2). Three single-shots are fired in sequence: a
1-usec, a 20-ms and a 350-usec. The 350-usec single-shot is taken through a delay
network to develop a 200-ns pulse that turns on the manual control trigger. By this
time, the switch has settled down and the trigger to perform the desired operation turns
on, resetting the manual control trigger.
Start Key (Figure 6.1-3)
If the CPU is in automatic and ready status, pressing the start key initiates machine
operation by turning off the master stop trigger and the program stop trigger. The
master stop trigger off conditions "not B cycle interrupt," allowing the computer to
proceed. If the system is in manual status, pressing the start key turns off the program
stop trigger.
Clear Key (Figure 6.1-4)
The clear key is only operative if the computer is in automatic status. Pressing the
clear key:
1. Fires a 1-usec single-shot to reset the clock and all channel registers of channels
that are not in manual status.
2. Resets CPU interlocks and registers.
3. Conditions circuits which allow zeros to be written into all storage locations.
The program counter controls the stepping through memory, with position 2 of the
PC indicating when all addresses have been zeroed. The turn-on of PC2 trigger will
turn on the master stop trigger at E10.
Display Storage (Figure 6. 1-5)
pressing the display storage key causes the address portion of the operator's panel
keys to be sensed, to determine the address in storage to be displayed. All 36-bit posi-
tions of the address will be displayed in the storage register. This is accomplished by:
(1) turning off the master stop trigger, (2) bringing the operator's panel keys to the
storage register in I time, and (3) suppressing "storage bus to storage register." The
address portion of the SR is routed through the adders and address switches, to the
address register. During E time, the SB is gated to the SR, which contains the 36 bits
of the desired address. If a tag or indirect addressing is specified in the operator's
keys, the contents of the effective address or the I-A address will be displayed.
Display Indicators
The display indicators key gates the true value of the sense indicators to the stor-
age for display (Figure 6.1-6).
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