Systems Reference Library - All about the IBM 1130 Computing ...

CCW Word 2Count Flags Command Code Data Addr15089 10 11 12 13 14 15Test I/0 0ReadMWriteMControlMSenseMTransfer in Channel0 0 0 0 0 0 0M M M M M 0M M M M M 0M M M M MM M M 0 0 00 0 0M = ModifierX = Bit ignoredI30202A1Figure 107. Command Code Assignmentpositions 0 through 7 of the last core storage word.Bit positions 8 through 15 in this word are all resetto 0's.WriteThis command causes data to be transferred fromcore storage to the device specified in the XIOinitialize write (start I/O) modifier bits. Data istransferred (two bytes per word) from ascendingcore storage locations beginning with the addressspecified in the CCW data address field. The numberof bytes transferred during the operation isspecified by the CCW byte count field.The write operation continues until the specifiednumber of bytes are transferred, or until the I/Odevice terminates the operation. If the byte count isodd, the last byte transferred is obtained from bitpositions 0 through 7 of the last core storage word.Bit positions 8 through 15 in this word are ignored.If an incorrect length condition occurs during awrite operation, the incorrect length indication isgiven to the program with the ending status unlessthe suppress length indication (SLI) flag is on in theCCW.ControlThis command causes the device specified by theXIO initialize write modifier bits to initiate a controloperation. The operation proceeds similar toa write, except that the command code modifier bitsreceived by the control unit are decoded to determinethe specific control function to be performed.In cases where the particular control functioncan be performed without any data transfer (immediatecommand), the control unit signals channel endas soon as it receives the command. The devicesignals device end after it has completed the controlfunction.A control command in which all six of the modifierbits in the command code are off performs as ano-op (no operation). A no-op causes the controlunit to respond with channel end and the device torespond with device end without causing any action.This ending status causes a unit status pending interruptto be generated. The unit address-status portion(word 2) of the channel status word (CSW) isavailable in the selector channel and may be read byan XIO sense device.SenseThis command performs in the same manner as aread, except that the data is obtained from statusindicators rather than from a record source.The status information is transferred to ascendingcore storage locations beginning with the addressspecified by the CCW data address field. Two bytesof status information are placed in each core storageword. The number of sense bytes transferred isspecified by the CCW byte-count and should beSelector Channel 203