IBM System/7 Functional Characteristics - All about the IBM 1130 ...

SYSTEM DATA FLOWData can enter or leave the System/7 through the operator station, the I/O modules, the5024 or a host system.Data entered through the operator station can consist of programs to be executed, datato be used by the program, or direct commands from the operator to the system. Dataleaving the system through the operator station can consist of messages to the operator ordata to be placed on the printer and/or paper tape.Data values, control information, and status information (collectively called data) are transferredin both directions between the I/O modules (including the 5024) and the processormodule. The System/7 processor can (1) evaluate and/or manipulate the data, (2) store thedata in main storage, or (3) send the data to a host processor for processing and/or storage.Generally, a host system transmits to System/7 the control programs, data, and parameterswithin which certain processes are to be maintained. In turn, System/7 sends to the hostsystem the collected data for processing, status information, or requests for new routinesto handle situations which cannot be serviced by the routines that currently reside in theSystem/7.POWER SYSTEM CONTROLPower ControlEach 5026 Enclosure in a System/7 configuration contains its own power system. A 5026Enclosure that contains a processor module is called a master unit; an enclosure that doesnot contain a processor module is called a remote unit. Power to remote units is normallycontrolled by the master unit. If, however, a remote unit loses power, its master unit doesnot lose power. A remote unit that loses power may give erroneous data, depending on theprogram that is executing at the time. The 5024 I/O Attachment Enclosure provides powerfor the line printer and 2502 card reader. The 5024's power is not controlled by the masterunit.Control SwitchesThe operator console on a master unit contains a power on/off switch and, optionally, anautomatic restart switch. The power on/off switch controls the power state of all modulesin the System/7 configuration with the execption of the 5024. The automatic restart switchcontrols the ability of the System/7 to restore power and perform an initial program load(IPL) when power is restored. The use of this switch is described later in this discussionunder "Power Failure."The operator console of a remote unit contains a power on/off switch and, optionally,an automatic restart switch. A local/remote switch is located behind the front cover panelimmediately below the operator console. This switch is used primarily for servicing theenclosure and its I/O modules. When the switch is set to the remote position, power tothe remote unit is controlled by the position of the power on/off switch on the masterunit. When the switch is set to the local position, power to the remote unit is controlledby the position of its power on/off switch, regardless of the power state of the masterunit. If power control of a remote unit is to be transferred from remote to local, theexecuting program should be modified prior to the actual transfer so that the modulesin the remote unit are not addressed. This should avoid unnecessary errors being sent tothe processor. Likewise, the program should be modified when power control is transferredfrom local to remote.The power on/off switch on a remote unit can be used to remove power from the remoteenclosure any time that the master unit is also powered on, regardless of the positionof the local/remote switch in the remote unit.1-6 GA34-0003