Word backspace circuit for buffered key entry device

Claim 2

In a key entry device having, a buffer memory having sequentially addressable column positions for storing characters or spaces keyed from a keyboard, a column counter incremented by keyboard operations for identifying the next buffer column position where an entry is to be made, means producing a scanning operation through the buffer in the order in which data columns are entered from the keyboard and identifying the column position being scanned, means comparing the count of the column counter and the column number identified by the scanning means for producing a Compare signal signifying that the scanning operation has reached the buffer column position where the next entry is to be made, and means for reading bits previously stored at said next column and for entering new bits from the keyboard, and means for successively subtracting one column from the count of the column counter for backspacing column by column in the buffer memory, wherein the improvement comprises, means to record in the scanning operation the occurrence of a space storing column, and means responsive to the occurrence of said Compare signal in the next column in the scanning sequence to stop the backspace operation in the column after said space storing column.

Claim 3

The key entry device of claim 1 further comprising means responsive to the occurrence of a column in the scanning sequence between said space containing column and said Compare signal for resetting said means to record a space to no longer signify the occurrence of a space containing column.

Claim 4

The key entry device of claim 2 wherein said means to record the occurrence of a space storing column comprises a latch connected to be set in response to the coincidence of a backspace key on said keyboard, an alpha key on said keyboard, and said space storing column.

Claim 5

The key entry device of claim 2 wherein a space is encoded as a 1 bit flag in a predetermined bit position of a group of bit positions making up a column position in the buffer and said means to record the occurrence of a space storing column comprises means connecting said latch to be set on the coincidence of said backspace key and said Space Flag.

Claim 6

The key entry device of claim 4 including means connecting said latch to be reset at a predetermined time in a column following a Space Flag column in the absence of a Compare signal.

Claim 7

The key entry device of claim 5 including means connecting said latch to change state only in the absence of said Compare signal.

Claim 8

In a key entry device having, a shift register bufFer memory having sequentially addressable column positions to store character and space entries from a keyboard in a serial sequence of a predetermined number of memory bits for each column, means defining a 1 bit output location for said buffer memory, a counter identifying the column of the buffer positioned at said output location, a column counter identifying the column location in the buffer where a next entry is to take place, and means for backspacing said column counter, whereby a next entry may be made at a column location containing a previously entered character or space, wherein the improvement comprises, a key on said keyboard identified as a word backspace key, a latch connected to be set on the coincidence of a signal from said word backspace key and a signal from said output location signifying that a column containing a space is present, means for resetting said latch on the occurrence of a subsequent column location at said output location other than said next column location in which an operation is to take place, and means responsive to the set state of said latch and the occurrence at said output location of said column location where the next operation is to take place for stopping a backspace operation.

Claim 9

In a key entry device having, a shift register bufFer memory having sequentially addressable column positions to store character and space entries from a keyboard in a serial sequence of a predetermined number of memory bits for each column, means defining a 1 bit output location for said buffer memory, a counter identifying the column of the buffer positioned at said output location, a column counter identifying the column location in the buffer where a next entry is to take place, and means for backspacing said column counter, whereby a next entry may be made at a column location containing a previously entered character or space, wherein the improvement comprises, a key on said keyboard identified as a word backspace key, a latch connected to be set on the coincidence of a signal from said word backspace key and a signal from said output location signifying that a column containing a space is present, means for resetting said latch on the occurrence of a subsequent column location at said output location other than said next column location in which an operation is to take place, and means responsive to the set state of said latch and the occurrence at said output location of said column location where the next operation is to take place for stopping a backspace operation.