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

I/0 Transfer BlockThe IOTB address must be stored at location 0008 before an initiate I/O is issued.After the initiate I/O instruction is accepted, the controller cycle steals the IOTB.Command Word0CommandIII3 8 15ZerosIIICarriage control1000 Reserved1001 Output print line1010 Output forms parameters1011 Output belt image1100 Disable printer attention interrupt1101 Reserved1110 Input forms parameters1111 Reserved(used only on a print command)The command word defines the operation to be performed. Bits 0-3 identify the command.Bits 4-7 are zero and bits 8-15 are used for carriage and control information on a printcommand. The commands are as follows:• Output Print 1001. When the print command is detected, the low order byte of thecommand word contains the carriage control byte.If the carriage control byte has a value from 1 to 132 (Hex 84), the carriagewill skip to the line indicated by the value.If the carriage control byte has d value greater than' Hex 84, the controllerwill treat the value as a negative number and cause a space of the twos-complement ofthe binary value.Therefore, a value of Hex 85 will cause spacing over 123 lines, and a value of Hex FFwill cause a one-line space. A value of Hex 00 causes no carriage motion. The line printerperforms the carriage space or skip prior to printing the line. Up to 66 words of printdata may be transferred for one print line.The ranges of skip/space values are shown as follows:Hex Binary Decimal01 0000 0001 Skip to line 1to84 1000 0100 Skip to line 13285 1000 0101 Space 123 linestoFF 1111 1111 Space 1 line00 0000 0000 No carriage motion• Output Forms Parameters 1010. This command initiates a one-wordcycle steal to the printer attachment. The high order byte is the binary number oflines on the form. The low order byte is the binary value at which the formoverflow bit in status word 1 is turned on. The word count is assumed to be 1 andis not checked.IBM 5024 I/O Attachment Enclosure 17- 19pnwn.m. • vimIII