GB2145303A

GB2145303A - Systems for transferring coded data

Info

Publication number: GB2145303A
Application number: GB08417152A
Authority: GB
Inventors: Alan John Jones; Malcolm Arthur Stubbs
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1983-08-17
Filing date: 1984-07-05
Publication date: 1985-03-20
Also published as: GB8322172D0; GB2145303B; GB8417152D0

Abstract

A system for transferring coded data from a first unit 1 to a second unit 3, in which the first unit 1 includes means 5 for producing a first signal, and the second unit 3 includes means 11, 7 responsive to the first signal to produce a second signal comprising a series of clock pulses. The first unit 1 further includes means 9 responsive to the second signal to produce a coded data signal for transmission to the second unit 3 synchronised with the clock pulses. By these means the provision of an accurate clock pulse generator in each unit 1, 3 is avoided. <IMAGE>

Description

SPECIFICATION Systems for transferring coded data This invention relates to systems for transferring coded data from a first unit to a second unit. In such a system the coded data must be transferred at a clock rate which is available in the second unit.

To this end each of the first and second units may contain an accurate, e.g. crystal controlled, clock pulse generator. It is an object of the present invention to provide a system of transferring coded data from a first unit to a second unit wherein the provision of an accurate clock pulse generator in each unit is avoided.

According to the present invention in a system for transferring coded data from a first unit to a second unit said first unit includes means to transmit a first signal to said second unit; said second unit includes means responsive to said first signal to transmit a second signal to said first unit comprising a series of clock pulses; and said first unit further includes means responsive to said second signal to transmit a coded data signal for transmission to said second unit synchronised with said clock pulses.

Preferably said first unit further includes means to transmit a further series of clock pulses to said second unit after transmission of said coded data signal to said second unit, and said second unit further includes means responsive to said further series of clock pulses to transmit an echo of said coded data signal to said first unit synchronised with the clock pulses of said further series.

Preferably said signals are transferred between said units as optical signals.

In one particular system in accordance with the invention said second unit is a programmable unit, said first unit is a programmer for said second unit, and said coded data signal comprises information for programming said second unit.

One system for transferring coded data from a first unit to a second unit in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing which is schematic diagram of the system.

Referring to the drawing, the system includes a first unit 1 which is a handheld programmer, and a second unit 3 which is a prepayment electricity meter. Each unit 1,3 includes a light source 5,7 and a photo-sensitive device 9, 11. Also included within each unit 1,3 are electrical means (not shown) effective to cause the light sources 5,7 to emit a light signal, and further electrical means (also not shown) responsive to the output of the photo-sensitive devices 9, 11. Each unit 1,3 also includes a clock means (not shown), the two clock means not being accurately of the same frequency.

In use the two units 1,3 are aligned with each other so that the photo-sensitive device 9, 11 on each unit is responsive to light signals emitted from the light source 7,5 on the other unit 3, 1. The light source 5 on the first unit is caused to emit a light signal containing a start code sequence which is transmitted to the photo-sensitive device 11 on the second unit 3. In response to this start code sequence, the light source 7 of the second unit is caused to emit a light signal comprising a series of clock pulses at the clock rate of the clock means within the second unit. These clock pulses are received by the photo-sensitive device 9 on the first unit 1, the first unit then subsequently transmitting from the light source 5 to the photo-sensitive device 11 a coded data signal synchronised to the clock pulses emitted by the second unit.This coded data signal contains data effective to program the second unit to, for example alter the amount of electricity delivered per unit charge, it being necessary to synchronise the coded data signal to the clock means within the second unit 3 in order to effect this programming.

The first unit 1 then transmits a series of clock pulses to the second unit 3 at the clock rate of the clock means in the first unit. In response the second unit 3 transmits an echo of the coded data signal back to the first unit 1 synchronised with the clock pulses received by the unit 3. This 'echo back' feature is included for security purposes to ensure that a person not in possession of a first unit 1 is not able to undetectably provide an unauthorised data signal to the second unit 3. Furthermore the 'echo back' feature provides a check that the correct data has been transmitted by the first unit 1. It will be appreciated that in a unit such as a hand held programmer it is particularly advantageous not to have to provide an accurate timing means within the device.Furthermore as the hand held programmer unit will generally be used with more than one prepayment meter unit, it is possible to use the programmer unit with meter units having different clock rates.

In an alternative application of the invention, the first unit 1 may be a programmer, and the second unit 3 an electronic multirate register having its own programmable clock which requires data to be transmitted to it for the purpose of clock setting and programming. In such an application data may also be transmitted from the register 3 to communicate the contents of the register.

It will be appreciated that whilst the examples described herebefore relate to a programmable unit, and a programmer unit, the invention is equally applicable to the transfer of any coded data signal between two units where it is necessary for the coded data signal to be synchronised to a clock within one of the units.

It will also be appreciated that although the units described hereinbefore are coupled optically, the invention is equally applicable to electrically coupled units.

1. A system for transferring coded data from a first unit to a second unit in which said first unit includes means to transmit a first signal to said second unit; said second unit includes means responsive to said first signal to transmit a second signal to said first unit comprising a series of clock pulses; and said first unit further includes means responsive to said second signal to transmit a coded data signal to said second unit synchronised with

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Systems for transferring coded data This invention relates to systems for transferring coded data from a first unit to a second unit. In such a system the coded data must be transferred at a clock rate which is available in the second unit. To this end each of the first and second units may contain an accurate, e.g. crystal controlled, clock pulse generator. It is an object of the present invention to provide a system of transferring coded data from a first unit to a second unit wherein the provision of an accurate clock pulse generator in each unit is avoided. According to the present invention in a system for transferring coded data from a first unit to a second unit said first unit includes means to transmit a first signal to said second unit; said second unit includes means responsive to said first signal to transmit a second signal to said first unit comprising a series of clock pulses; and said first unit further includes means responsive to said second signal to transmit a coded data signal for transmission to said second unit synchronised with said clock pulses. Preferably said first unit further includes means to transmit a further series of clock pulses to said second unit after transmission of said coded data signal to said second unit, and said second unit further includes means responsive to said further series of clock pulses to transmit an echo of said coded data signal to said first unit synchronised with the clock pulses of said further series. Preferably said signals are transferred between said units as optical signals. In one particular system in accordance with the invention said second unit is a programmable unit, said first unit is a programmer for said second unit, and said coded data signal comprises information for programming said second unit. One system for transferring coded data from a first unit to a second unit in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing which is schematic diagram of the system. Referring to the drawing, the system includes a first unit 1 which is a handheld programmer, and a second unit 3 which is a prepayment electricity meter. Each unit 1,3 includes a light source 5,7 and a photo-sensitive device 9, 11. Also included within each unit 1,3 are electrical means (not shown) effective to cause the light sources 5,7 to emit a light signal, and further electrical means (also not shown) responsive to the output of the photo-sensitive devices 9, 11. Each unit 1,3 also includes a clock means (not shown), the two clock means not being accurately of the same frequency. In use the two units 1,3 are aligned with each other so that the photo-sensitive device 9, 11 on each unit is responsive to light signals emitted from the light source 7,5 on the other unit 3, 1. The light source 5 on the first unit is caused to emit a light signal containing a start code sequence which is transmitted to the photo-sensitive device 11 on the second unit 3. In response to this start code sequence, the light source 7 of the second unit is caused to emit a light signal comprising a series of clock pulses at the clock rate of the clock means within the second unit. These clock pulses are received by the photo-sensitive device 9 on the first unit 1, the first unit then subsequently transmitting from the light source 5 to the photo-sensitive device 11 a coded data signal synchronised to the clock pulses emitted by the second unit.This coded data signal contains data effective to program the second unit to, for example alter the amount of electricity delivered per unit charge, it being necessary to synchronise the coded data signal to the clock means within the second unit 3 in order to effect this programming. The first unit 1 then transmits a series of clock pulses to the second unit 3 at the clock rate of the clock means in the first unit. In response the second unit 3 transmits an echo of the coded data signal back to the first unit 1 synchronised with the clock pulses received by the unit 3. This 'echo back' feature is included for security purposes to ensure that a person not in possession of a first unit 1 is not able to undetectably provide an unauthorised data signal to the second unit 3. Furthermore the 'echo back' feature provides a check that the correct data has been transmitted by the first unit 1. It will be appreciated that in a unit such as a hand held programmer it is particularly advantageous not to have to provide an accurate timing means within the device.Furthermore as the hand held programmer unit will generally be used with more than one prepayment meter unit, it is possible to use the programmer unit with meter units having different clock rates. In an alternative application of the invention, the first unit 1 may be a programmer, and the second unit 3 an electronic multirate register having its own programmable clock which requires data to be transmitted to it for the purpose of clock setting and programming. In such an application data may also be transmitted from the register 3 to communicate the contents of the register. It will be appreciated that whilst the examples described herebefore relate to a programmable unit, and a programmer unit, the invention is equally applicable to the transfer of any coded data signal between two units where it is necessary for the coded data signal to be synchronised to a clock within one of the units. It will also be appreciated that although the units described hereinbefore are coupled optically, the invention is equally applicable to electrically coupled units. CLAIMS

1. A system for transferring coded data from a first unit to a second unit in which said first unit includes means to transmit a first signal to said second unit; said second unit includes means responsive to said first signal to transmit a second signal to said first unit comprising a series of clock pulses; and said first unit further includes means responsive to said second signal to transmit a coded data signal to said second unit synchronised with said clock pulses.

2. A system according to Claim 1 in which said first first unit further includes means to transmit a further series of clock pulses to said second unit after transmission of said coded data signal to said second unit, and said second unit further includes means responsive to said further series of clock pulses to transmit an echo of said coded data signal to said first unit synchronised with the clock pulses of said further series.

3. A system according to either one of the preceding claims in which said signals are transferred between said units as optical signals.

4. A system according to any one of the preceding claims in which said second unit is a programmable unit, said first unit is a programmer for said second unit, and said coded data signal comprises information for programming said second unit.

5. A system according to Claim 4 in which said second unit is a prepayment electricity meter, and said first unit is handheld programmer.

6. A system according to Claim 5 in which said coded data signal contains data effective to program said meter to alter the amount of electricity delivered per unit charge.

7. A system according to Claim 4 in which said second unit is an electronic multirate register containing a programmable clock, and said coded data signal contains data for setting and programming said clock.

8. A system for transferring coded data from a first unit to a second unit substantially as hereinbefore described with reference to the accompanying drawing.