Writing a Record of Information
Information is written on the tape by giving a MWB or MWA command. This sets a write binary or a write alphanumeric into the TC and selects the unit. A motion select command is executed immediately if the TC is free, otherwise, the command waits until it can be executed. Normal programming can continue after the MWA or MWB is given for approximately 5 milliseconds. At this time, an MPS order is given and the program pauses until information can be written. When the MPS is restarted, information is transferred to the TC buffer from the IO. If no flags have been set, the following instruction is skipped.
Three-quarter inches of blank tape is written by giving either the MWA or MWB order. An end of file is written as follows: 1) Four MWA commands write three inches of blank tape. 2) Then end of file character is written by giving the MPS order.
Information is read and checked for correct parity while writing.
If too many program steps are given between the motion select command, MWA or MWB and the first MPS, the unit will deselect (or disconnect). The MPS is then a no-operation command.
Writing Program
As an example, a program to write k words in binary format from storage beginning in register A, using tape unit number 04, is shown. The following program is written in standard FRAP language. The program begins in register enterwrite.
| enterwrite | mec | ,clear flags initially |
| mwb 400 | ,73000000464 | |
| lir x/-k+1 | ,initialize index register x | |
| b | lio x/a+k-1 | ,begin loop |
| mps | ,wait for TC then write C(Z) | |
| jmp c | ,error | |
| spx x/1 | ,add 1 to index register x | |
| jmp b | ,return of loop | |
| jmp done | ,record written | |
| c | mec | ,tape error |
| ril 1 | ||
| spi | ||
| jmp rwcstop | ,read-write error or tape fault | |
| ril 1 | ||
| spi | ||
| jmp b+3 | ,tape end | |
| hlt | ,tape parity | |
| done | ,resume programming |
Reading Information