Method and a device for reading out keyboard keys

1. A method for reading out keys of a keyboard, in particular a keyboard of an automatic teller machine, said keys being arranged according to a row and column set-up of a matrix, wherein a first scanning pattern for reading out said keys is applied to said keyboard, said method comprises a first series of steps consisting of:

(a) randomly generating said first scanning pattern, which comprises for each of said rows and columns a first read-out value to be applied onto said row respectively said column;

(b) applying said first scanning pattern onto said rows and columns during at least a first minimum time period;

(c) applying a verification routine in order to determine if the actual values of each row and column correspond to those applied by the first scanning pattern and to identify those rows and columns for which the actual value does not correspond to the one applied by the first pattern,

(d) repeating, after said first time period has lapsed, said first series of steps if no rows and columns have been identified by said verification routine;

characterised in that said method further comprises;

(e) temporarily storing a pointer pointing to said rows and columns identified during said verification routine;

(f) applying a second series of steps which is started after storing said pointer, said second series of steps comprises:

(g) randomly generating, after said first time period has lapsed, a second scanning pattern comprising for at least each of said rows and columns indicated by said pointer a second read-out value to be applied onto said rows and columns;

(h) applying said second scanning pattern to said rows and columns during at least a second minimum time period;

(i) monitoring said identified rows and columns by using said second pattern in order to confirm as activated keys those keys located on said identified rows and columns.

2. A method as claimed in claim 1 , characterised in that said first and second time period are randomly determined.

3. A method as claimed in claim 1 , characterised in that said first series of steps is subsequently applied for a predetermined number of times, each time that the verification routine identifies a row and a column during said subsequent application of the first series of steps a counter is incremented for the identified row and column, said counter being provided for generating a storage signal upon reaching a predetermined number, said pointer being stored under control of said storage signal.

4. A method as claimed in claim 1 , characterised in that said monitoring is interrupted upon establishing that the actual values of the monitored rows and columns correspond to those applied by the second scanning pattern, said interruption being followed by a return to said first series of steps.

5. A method as claimed in claim 1 , characterised in that said confirmation is realised by applying a further verification routine in order to determine if the actual values of at least those rows and columns indicated by said pointers correspond to those values applied by the second scanning pattern and to identify those rows and columns for which the actual value does not correspond to the one applied by the second pattern.

6. A device for reading out keys of a keyboard, in particular a keyboard of an automatic teller machine, said keys being arranged according to a row and column set-up of a matrix, said device comprising a scanning pattern generator provided for generating a first scanning pattern allowing to readout said keys, said device also comprises first means for applying said first scanning pattern to said keys during at least a first minimum time period, said device further comprises a random generator provided for randomly generating said first scanning pattern, which comprises for each of said rows and columns a first read-out value to be applied onto said row respectively said column, said device also comprises a verification member provided for applying a verification routine which comprises a verification if the actual value of each row and column corresponds to the one applied by the first pattern and an identification of those rows and columns for which the actual value does not correspond to the one applied by the first pattern, characterised in that said verification routine further comprises a temporary storage of a pointer to said identified rows and columns and their actual value, said scanning pattern generator being further provided for generating randomly, after said first time period has lapsed, a second scanning pattern comprising, for at least each of said rows and columns indicated by said pointer a second read-out value to be applied onto said row respectively said column, said first means being also provided for applying said second scanning pattern onto said keys during at least a second minimum time period, said verification member being further provided for monitoring said identified rows and columns by using said second pattern in order to confirm as activated keys those keys located on said identified rows and columns.