The ability to index forms vertically under program control to a predetermined print line is provided by the Page Length Control specify feature for the terminal printer. Special links and preprinted forms containing index marks are not required to make this feature operational.
When a valid Forms Feed (FF) order is encountered in the buffer during a print-out, the form indexes to a predetermined line. Printing begins on the predeter-mined line; the first print position, the buffer location containing the FF character, is printed as a space character. Printing and indexing continues until the printout is terminated. The printer is "busy" while printing and indexing.
4-2 Processor Display/Printer Adapter Component Description
There is no limit on the number of FF orders that can be included in the printer buffer or on the frequency of their occurrence. However, for an FF order to be considered valid and thus initiate indexing, the printer must be equipped with the Page Length Control/VFC feature, and FF characters must be placed in buffer locations corresponding to the first position of a print line in a field designated either print or non-print. This can be accomplished by placing the FF character in the following locations:
1. The first character after the WCC in a Write or Erase/Write data stream to the printer.
2. After a valid NL or CR order.
3. The first character position of any print line (for example, in character posi-tion 41 in a buffer with a line-length format of 40 characters per line speci-fied, or in character position 133 in a buffer without a line-length format specified.)
An FF order in any other position in the printer buffer or in a printer without Page Length Control/VFC is considered invalid: the index operation is not exe-cuted, and the FF character prints as a space character except when the FF order is located in a non-print field. A valid FF order prints as a space character.
During printing, if a valid FF order is encountered when the form is located at the predetermined index stop line, the index operation will be executed, and a blank form will result. The printer will not skip a blank form.
Before beginning Page Length Control/VFC printouts, forms must be loaded in the printer and aligned to the print line where indexing should stop and printing begin. If the forms are not aligned properly while initially being loaded, all forms will be misprinted. The Page Length Control/VFC circuitry synchronizes with the index stop line on the form as the cover is closed and the printer goes from Not Ready to Ready. If the cover must be raised or if a Not Ready condition occurs, the form must be checked to ensure that the index stop line is in the prop-er position before reclosing the covprop-er.
The two Page Length Control/VFC selector switches must be set to the number corresponding to the total number of print lines from one index stop line to the next for each index stop lines. When uniform length forms are used, the setting for the switches is computed by multiplying the forms length in inches by the 6 or 8 lines-per-inch setting. (For example, when II-inch forms are installed on the terminal printer, the switches should be set at 66.) The maximum form length, fold-to-fold when operating at 8 LPI, is 12.375 inches.
Programming Notes:
1. If an NL order and an FF order appear on the last line of a terminal printer printout and VFC is installed, subsequent printing will begin on a new form.
2. Page Length Control is synchronized when power is applied or when the FF switch is pressed.
Chapter 4. Printer 4-3
Chapter 5. Local Operations
Selection
The Display/Printer Adapter operates program and data stream compatible with 3274-1B Control Unit. Data and control information is transferred in bursts of up to 256 bytes per burst. The Display/Printer Adapter is considered to be a part of the byte multiplexer channel of the 4361 Processor with channel address zero.
The 4361 Processor detects the SIO in the instruction stream and determines the attachment based on the channel, control unit, and device address. The address range from 009 to OIF is reserved for the devices on the Display/Printer Adapter and the user diskette.
The configuration is set up by selecting the Native Display and Printer
Configurator from the Customer Manual Operation functions. See Operator's Library: IBM 4361 Processor Operating Procedures, GA33-1570.
The following parameters have to be entered per port of the coax connectors:
• Device type
• Keyboard/language combination
One or two keyboard language combinations may be ordered and are dis-played on the configuration picture.
• Device address out of the range of 009-01F Any double definition or out-of-range is checked.
With the next IML, any change in the configuration becomes active. Removing a device physically does not necessarily require a change of the configuration. The open port answers with unit check and IR when addressed.
The channel program controls all Display/Printer Adapter operations by transmit-ting information. This information consists of:
1. An address, which selects the device (display or printer) attached to the Dis-play/Printer Adapter.
2. Command bytes, which specify the type of operation to be performed by the Display/Printer Adapter for that device.
3. Data bytes, which are either stored in the printer buffer for ultimate use by the selected device as display or printout or are decoded as orders and used by the Display/Printer Adapter for formatting the buffer.
4. Various control signals.
Status bytes, which are automatically generated by the Display/Printer Adapter, inform the channel program:
1. Of the general condition of the Display/Printer Adapter and selected device at various stages of command operations.
Chapter 5. Local Operations 5-1