Section 4.3

Paper Tape Readers & Punches

(See also general description in 4.1.)

4.3.1

The following types of paper tape reader and punch are at present in use on Orion:

Readers:
I.C.T. TR5 (300 characters/second)

I.C.T. TR7 (1000 characters/second)

Creed 25 (33 characters/second)

Punches:
Creed 3000 (300 characters/second)

Teletype (63 or 110 characters/second)

Of these Creed 3000 is for 7 track only on Orion, the others being 5 or 7 track as separate versions or by switch selection.

These devices are directed by a paper-tape Control Unit which can control up to four devices, in any combination of paper-tape readers, punches, or Flexowriters (a Flexowriter counting as two devices). As only one transfer at a time can take place on each Control Unit, at least two such units are normally provided. An Orion installation must have at least one paper-tape reader, one punch, and one Flexowriter.

4.3.2 Modes

Reading and punching of paper tape are effected by compound instructions such as:

140.8 0 *FR1 |read (5 track) 10 chars
142 BUFFER 10 |into BUFFER onwards

140.21 0 *SPl |punch (7 track) up to NL or 10
142 BUFFER 10 |characters at most from BUFFER

The modes associated with paper tape devices are:

Readers:
1   read 7 track up to NL but most Y characters
2   read 7 track Y characters
8   read 5 track Y characters
Punches:
21 punch 7 track up to NL but at most Y characters
22 punch 7 track Y characters
28 punch 5 track Y characters

4.3.3 4.3.4 Parity

On 7 track paper tape the 5th track is used only for checking purposes and is punched so as to make the total number of holes in each character odd. When reading, the bit corresponding to this 'parity' track is checked to ensure that the character has been read correctly and is then removed, the remaining six bits giving the correct internal code without conversion. On output the control unit examines the character to be punched and inserts a parity bit if required. The 7 bit character is then transmitted to the punch where, before punching, the electronics check parity. The incident PARITY FAIL is signalled in the event of failure of this test.

5 track tape has no parity check and in this code the internal values are not taken as the direct bit equivalent of the punching.

The code lists for 5 and 7 track paper tape are shown in section 4.3.3.

4.3.5 General Description

Readers

Tape is fed from a loose coil placed in standard tape trough into a bin, or, when great lengths are involved (TR7 only), fed between two spools in a servo-controlled system. The tape is driven by rollers past the photo-electric reading head. By this means the tape is read after which the data are transferred to the core store via the control unit.

Punches

The tape feeds from a spool and is pulled through the punch unit in a series of jerking movements. When the tape is stationary in the punching position a die block pushes the tape upwards onto the punch pins which have already been set to correspond to the required character (in the case of the Teletype the punch pins move downwards onto the paper). The paper is pierced by the pins then lowered and advanced 1/10" to the next position for another character to be punched.

On the Creed 3000 only, the tape is read back by a photo-electric sensing device after three punching cycles. A comparison is made of the character sensed and that which should have been punched three cycles previously. Failure of this test causes the incident PARITY FAIL, the punch being disengaged and the job halted.

If, due to a programming error, the value of a character to be punched on a 5 track punch lies in the range 32-63, a logical not-equivalent operation is performed between the m.s. bit of the six and the l.s. The l.s. 5 bits of the result are then taken as the value of the character to be output.

e.g. 101010 becomes 01011
101011 becomes 01010

4.3.6 Timing of Operations

The machine cycle times are:

TR5 - 3 ms Creed 25 - 30 ms Teletype (63) - 16 ms

TR7 - 30 ms Creed 3000 - 3 ms Teletype (110) - 9 ms

Maximum operating speed will be maintained if the next read/punch instruction is issued not later than one cycle time from commencement of reading/punching the last character indicated by the previous read/punch instruction. (Actually about 1 ms earlier than this because of time spent in the time sharer). Because of sharing time with other programs the amount of mill time available to the program during a peripheral transfer is uncertain, but, if the program requires to use more mill time than indicated above, the device will operate at less than full speed.

4.3.7 Controls, Indicators and Incidents

The reader display has the following controls and indicators:

ENGAGE        Push button and indicator
DISENGAGE    Push button and indicator
MAINS             Push button and indicator

SELECT Push button and indicator
Illuminated blue during transfers, otherwise white.

7-TRACK/5-TRACK Push button and indicator
The mode is indicated by whichever half is illuminated: yellow for 7-track, blue for 5-track. Pressing the button changes the mode.

Reading Incidents:

Message	Cause	OMP default action
ADDRESS FAIL	Parity failure detected in address of working store register or address from which transfer is being attempted	Job halted. Reader disengaged. Message printed on Flexowriter
DISABLED	Mains supply switched off Door or cover open Paper tear	Job halted. Reader disengaged. Message printed on Flexowriter
PARITY FAIL	Even no. of holes detected in 7 track paper tape due to mis-punching or misreading	Job halted. Reader disengaged. Message printed on Flexowriter
WRONG MODE	Program or operating error in using incorrect mode	Job halted. Reader disengaged. Message printed on Flexowriter
OMP	Failure during input of primary input directives	Job halted. Reader disengaged. Further message on Flexowriter (as above) giving cause.

* TR7 only

The following controls and indicators apply to the Creed 3000 and Teletype punches:

ENGAGE	Push button and indicator
DISENGAGE	Push button and indicator
MAINS	Push button and indicator
SELECTED	Indicator	Illuminated blue when punching
TAPE LOW	Indicator	Illuminated amber when tape supply is low or if tape breaks before reaching the tape sensing device
RUN OUT	Push button and indicator	Pressing this button causes UC characters to be punched

Punching Incidents

Message	Cause	OMP default action
ADDRESS FAIL	Parity failure detected in address of working store register or address from which transfer is being attempted	Job halted. Punch disengaged. Message printed on Flexowriter.
DISABLED	Mains supply switched off Cover of punch raised Tape breaks or runs out	Job halted. Punch disengaged. Message printed on Flexowriter.
PARITY FAIL	Even no. of holes found on 7 track punch. *Or failure of read-back check.	Job halted. Punch disengaged. Message printed on Flexowriter.
WRONG MODE OPERATOR	Program error Tape supply low	Punch disengaged. Message printed on Flexowriter.
OUTPUT LOST ON	Failure of OMP initiated transfer	Message printed on Flexowriter.

* Creed 3000 only

4.3.8 End of Tape

The end of tape, or a break in the tape, will be detected only by the TR7 reader operating in the "with spooling" mode: the job will be halted and a DISABLED incident signalled. The exact result of reading past end of tape on the TR5 reader and the TR7 "without spooling" depends upon the physical end of tape itself. For a character to be sensed illumination at the sprocket hole track must switch off and then on. If the paper is torn straight across a hole or across the gap between characters all tracks will be illuminated and an erase character sensed. No further characters will be sensed as the sprocket hole illumination stays on. If the tear is diagonal the last few characters sensed may be incorrect as extra holes are illuminated, or may give rise to parity failure (7 track only), or may end with an erase character as above. A further possibility is that the last character may be correctly read but no further characters sensed. Unless the end of tape causes parity fail, the reader will appear to be permanently busy - in a state to read the next character presented. No error indication will be given to the operator. Such an occurrence will necessitate a restart and programmers should therefore avoid the possibility of reading past end of tape by providing a means of detecting an end of data configuration on a paper tape.

Punches halt when the tape supply reaches a pre-determined low level. If the tape breaks whilst the punch is operating, a DISABLED incident is signalled and the device disengaged.

4.3.9 Orion 2 Differences

The information in the preceding sections 4.3.1. etc. refers in general to both Orion 1 and Orion 2. Described here are the differences to be noted when reading these for Orion 2.

Section 4.3.1. The Creed 3000 and I.C.T. TR7 are not available. Each peripheral has its own control unit.