LINE PRINTER ON-LINE

The on-line off-line status of the Line Printer may be tested by the program, refer to Se ction 7.

The rated speed of the Line Printer is 1000 lines per minute. The effective speed is governed by the line content, the computing time, and the between line skipping requirements, of the particular application.

8.3.1.1 DATA TRANSFER.

a. Data Flow. The data to be printed is read, from Core Memory; a word at a time to the Dni-Record Interface, and on through the Magnetic Tape Console to the Core Buffer in the Line Printer. When the Core Buffer is full, and the previous line has been printed, the printer skips, and printing is initiated. Immediately after each word has been read out of Core Memory, the operand portion of the Interface Instruction register is incremented, and the Interface Word Counter is decremented. When the last word to be printed has been transferred to the

Printer Core Buffer, the operation is complete, and the Interface requests a Uni-Record Interface Not Busy Interrupt.

b. Error Checking. Parity error checking is performed in the M register and at the Magnetic Tape Console. No parity checking is done in the Line Printer.

8. 3. 1. 2 LINE PRINTER INSTRUCTION OPERATION.

Section VIII Paragraph 8. 3. 1. 2

For instruction format, refer to paragraph 8. 2. 1. 4. Mnemonic PRNT, PR TCTL a. Output (Y6 OFF) - PRNT. An Output instruction that addresses the Line Printer with the Y6 bit OFF, will cause up to 17~:~ consecutive words to be trans-ferred from Core Memory to the Line Printer, beginning with the effective operand address. The number of word(s) transferred is specified by the Uni-Record Interface Word Counter, which must be preloaded. When fewer than 17 words are specified, the remainder of the line will be padded out with blanks.

b. Output (Y6 ON) - PRTCTL. An Output instruction with the Y6 bit ON that addresses the Line Printer is a control instruction. It will turn Vertical Format to Automatic mode if the word at the effective address begins with a 1. If the effective address references a word that begins with any character except 1 or 2, the Line Printer will be rendered inoperative. Restoring the unit to an operative state may be accomplished by manual means only. Since the Word Counter is not loaded for these operations, it is ignored and undisturbed.

Vertical Formatting is turned to Controlled mode by executing an Output instruc-tion with Y6 ON, referencing a word beginning with a 2.

c. Vertical Format (Skipping). Vertical spacing is determined by program or automatic format control, utilizing a pre-punched, 8 channel, vertical format con-trol tape. Vertical spacing is 6 lines to the inch, manually adjustable to 8.

(1) Controlled Vertical Format. In the Controlled Format mode, the three least significant bits of the most significant character in the first word transferred to the Line Printer (carriage control character) specify a channel. Channels are specified with the characters '/J through 7 for Channels 1 through 8, respectively.

The carriage will advance the paper until a hole in the specified channel on the control tape is sensed, at which time the line will be printed. The second charac':"

ter transferred will be printed in the first hammer position. The carriage control character will not be printed, however, up to 132 consecutive characters wil1.be printed, as specified by the Word Counter. For each line printed, the Word Counter must be loaded and an Output instruction is sued.

~:~If Controlled Vertical Format is used, no matter what number is loaded into the Interface Word Counter, no more than 133 characters will be transferred to the Line Printer. If Automatic Vertical Formatting is used, the Uni-Record Inter-face Word Counter may specify any number of words (lines).

Section VIII

Paragraph 8.3.1.2 (Cont.)

(2) Automatic Vertical Format. The Automatic Forn1at mode allows con-tinuous printing without beginning each line with a format control character.

Channel 8 on the vertical format tape is selected and the skipping will be dictated by the contents of that channel. Any number of consecutive words, and thus lines, may be specified by the Interface Word Counter. Sixteen words and four charac-ters from the seventeenth word will be printed. The remaining four characcharac-ters of the seventeenth word will be printed as the first four characters of the next line, which will then fill out with 16 more words. The Uni-Record Interface remains Busy until all specified words have been transferred.

Vertical format channels 1 and 2 are used with the manual Line Printer controls, paragraph 8.3.2.

d. Timing. The rated printing speed is 1000 lines per minute. The effective speed varies with the skipping, line content, and computing requirements.

For each line skipped, there is a 25% loss of speed. For example, double space printing will print at 800 lines per minute.

Printing successive lines containing characters from the last quadrant of the print drum will slow the printing speed down to 500 lines per minute. The characters on the Print Drum are divided into four quadrants, table 8 -2.

In the case where more than one line is specified, the program may need to know when a line has been transferred out of the Central Processor. This may be accomplished through the use of the Interface Word Counter and/or the Interface Instruction register. Seventeen words (one line) will be transferred from the Central Processor at a maximum rate of one line every 59.8 milliseconds.

When one line at a time operation is specified,the Uni-Record Interface remains Busy only while data is being transferred to the Printer Buffer (less than 3 milli-seconds). Therefore, the program is free to use other Uni-Record devices during the 56.8 milliseconds of print time. However, to maintain maximum effective printing speed, the next Output instruction must be issued within 59.8 milliseconds.

Se ction VIII

Any error will terminate the operation.

Error recovery procedures are governed largely by the application, however, the Interface Instruction register and the Interface Word Counter may be used to indicate the point of termination.

Section VIII

Par a g r a ph s 8. 3. 2 to 8. 3. 2. 2