Information handling and control systems

A battery (+V) operable information handling and control system, for example for an automotive vehicle electrical system, has a central unit (10) and a number of remote units (20) each connected to the central unit (10) by a respective signalling link (40). The central unit (10) includes processing and control circuitry (13) and power supply circuitry (11) which are turned on to operate the processing and control circuitry (13) in an active mode of the system and are turned off in a sleep mode of the system. During the active mode the processing and control circuitry (13) applies a clock pulse voltage to a data line (41) in each signalling link (40). One of the clock pulse lines (41) is connected to power supply control circuitry (12) in the central unit (10) and to activation voltage drive circuitry (80) in the respective remote unit (20). When the system is in the sleep mode the activation voltage drive circuitry (80) can be enabled by operation of a activation switch (60, 61) connected to that remote unit (20) so as to apply to that clock pulse line (41) an activation voltage, substantially the battery +V voltage (12 volts) and lower than the clock pulse voltage (30 volts). The power supply control circuitry (12) is enabled by the activation voltage so as to turn on the power supply circuitry (11) and the activation voltage drive circuitry (80) is then disabled responsive to the clock pulse voltage consequently applied at the start of the active mode.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to information handling and control systems, for 
example for inclusion in automotive vehicle electrical systems. 
In particular this invention relates to an information handling and control 
system comprising a central unit and a plurality of remote units each 
connected to the central unit by a respective signalling link, the system 
being operable by battery means when connected to the central unit and to 
at least some of the remote units, wherein the central unit includes 
processing and control means and power supply means therefor. 
2. Description of Related Art 
An example of such a system in the form of an automotive vehicle electrical 
system is known from the article "Multiplexing for the automotive 
industry" by W. R. Betts in GEC REVIEW, Vol. 2, No. 1, 1986 at pages 32 to 
36. 
In order to minimize current drain and conserve the capacity of the battery 
means in such a system it is desirable to provide for a sleep mode of the 
system in which the power supply means in the central unit are turned off, 
as well as an active mode of the system in which the power supply means 
are turned on to operate the processing and control means. In such a 
system where the user has access only to the remote units it is necessary 
to provide means for the user to bring the system out of its sleep mode by 
activation from a remote unit. For example in an automotive vehicle 
electrical system, it may be desirable to provide for activation from any 
of a number of different switches such as an ignition switch or sidelight 
switch which may be connected to the same remote unit, a door opening 
switch connected to another remote unit, and possibly a system test mode 
switch connected to yet another remote unit. 
It is possible for the remote activation means to include a dedicated 
activation wire, extra to the signalling links, between the central unit 
and any remote unit from which the user is to be able to bring the system 
into its active mode. However there is a significant cost disadvantage in 
providing such extra activation wires together with associated connector 
pins and additional means for noise suppression. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a system with means for remote 
activation but without a dedicated activation wire, and the invention is 
based on the idea of temporarily applying to an existing line of a 
signalling link an activation voltage level which is different from the 
active mode operation voltage on that line. 
According to the invention there is provided an information handling and 
control system comprising a central unit and a plurality of remote units 
each connected to the central unit by a respective signalling link, the 
system being operable by battery means when connected to the central unit 
and to at least some of the remote units, wherein the central unit 
includes processing and control means and power supply means which are 
turned on to operate the processing and control means in an active mode of 
the system and are turned off in a sleep mode of the system, wherein 
during said active mode the processing and control means applies an 
operation voltage in pulse form to a data line in each signalling link, 
wherein one of said data lines is connected to power supply control means 
in the central unit and to activation voltage drive means in the 
respective remote unit, the power supply control means and the activation 
voltage drive means being fed by the battery means during both the sleep 
mode and the active mode, wherein when the system is in the sleep mode the 
activation voltage drive means can be enabled by operation of an 
activation switch connected to that remote unit so as to apply an 
activation voltage, different from said operation voltage, to that data 
line, and wherein the power supply control means is enabled responsive to 
the activation voltage so as to turn on the power supply means and the 
activation voltage drive means is then disabled responsive to the 
operation voltage consequently applied at the start of the active mode. 
Reliability of the system according to the invention may be enhanced by 
arranging that when the system is in the active mode the activation 
voltage drive means are maintained disabled responsive to the pluse form 
operation voltage. This may be achieved in an advantageously simple and 
economical manner by provision in the activation voltage drive means of a 
bipolar transistor having its activation voltage drive means of a bipolar 
transistor having its emitter fed by the battery means, its collector 
connected to said data line, and its base connected to said activation 
switch and to a capacitor, and the arrangement of the activation voltage 
drive means being such that when the system is in the sleep mode the 
capacitor is discharged and the transistor is turned off, such that 
responsive to operation of the activation switch when the system is in the 
sleep mode the transistor is turned on so as to apply said activation 
voltage, less than said operation voltage, to said data line, such that 
responsive to the operation voltage consequently applied at the start of 
the active mode the capacitor is charged via the transistor collector-base 
diode so as to turn off the transistor, and such that when the system is 
in the active mode the capacitor is maintained charged responsive to the 
pulse form operation voltage so as to maintain the transistor turned off. 
The battery means in the system according to the invention may apply the 
same battery voltage to the central unit and to the remote units, said 
activation voltage being substantially said battery voltage, and said 
power supply means converting said battery voltage to a higher voltage to 
be applied as said operation voltage to the data lines. For example, when 
the system according to the invention is incorporated in an automotive 
vehicle electrical system the battery voltage will be 12 volts and the 
higher operation voltage may be 30 volts. Such a higher operation voltage 
has noise immunity and other advantages as described in the 
above-mentioned GEC REVIEW article. 
The system according to the invention may be arranged such that when it is 
in the active mode the power supply control means in the central unit are 
maintained enabled responsive to the pulse form operation voltage, and 
furthermore such that it reverts to the sleep mode when the power supply 
control means are disabled responsive to discontinuation of the pulse form 
operation voltage. This arrangement whereby the control and processing 
means simply discontinues the pulse form operation voltage for the purpose 
of turning off the power supply means, rather than the control and 
processing means having to provide a special output signal for this 
purpose, ensures reliable switching of the system between the active mode 
and the sleep mode. 
The arrangement described in the previous paragraph may be simply and 
economically achieved by providing that the power supply control means 
have an input connected to said data line and to a capacitor, the 
arrangement of the power supply control means being such that when the 
system is in the sleep mode that capacitor is discharged, such that 
responsive to said activation voltage that capacitor is charged above a 
reference voltage value whereupon the power supply control means output 
turns on the power supply means, such that that capacitor is maintained 
charged above said reference voltage value responsive to the pulse form 
operation voltage, and such that responsive to discontinuation of the 
pulse form operation voltage that capacitor discharges to below said 
reference voltage value whereupon the power supply control means output 
turns off the power supply means. 
The system according to the invention may be arranged such that at least 
some of the remote units having said battery means connected thereto have 
loads connected to them and at least some of the remote units have 
function switches connected to them, said loads being indirectly operable 
by said function switches via the processing and control means in the 
central unit. For example when incorporated in an automotive vehicle 
electrical system these loads may include the ignition, lamps and motors. 
Although remote activation of the system according to the invention may be 
provided for from one or more switches specially provided for that 
purpose, it is clearly advantageous in a system as described in the 
previous paragraph for the user to be able to remotely activate the system 
by operating one of the function switches. This may be achieved in such a 
system wherein each said signalling link said data line is a clock pulse 
line with said operation voltage in pulse form constituting clock pulses, 
wherein each said signalling link also includes a signal line which is 
connected to a corresponding one of a plurality of demultiplexer channels 
in the respective remote unit in an assigned time slot under control of 
said clock pulses, wherein each of said loads and said function switches 
are connected to a respective said demultiplexer channel, and wherein said 
activation switch is one of said function switches, the arrangement being 
such that when the system has been put into the active mode responsive to 
operation of the combined activation-function switch, the operated 
function condition of said combined activation-function switch is then 
detected by the processing and control means via the respective signal 
line. 
In a system as described in the previous paragraph, at least two said 
combined activation-function switches may be connected in parallel to said 
activation voltage drive means in the same remote unit, in which case 
means are provided for maintaining mutual isolation of the demultiplexer 
channels to which those combined activation-function switches are 
connected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, there is shown a star wired system with an 
intelligent, central, master unit 10 and a number of non-intelligent, 
remote, slave units 20. The system is operable by battery means +V when 
connected to the central unit 10 and via fuses 30 to the remote units 20. 
A low current signalling link 40 is connected from the central unit 10 to 
each remote unit 20. Manually operable electrical switches, sensors, and 
high current loads (not shown in FIG. 1) are connected to the remote units 
20 and their interaction is controlled from the central unit 10 by means 
of time slot assignment multiplex. 
Referring now to FIG. 2, the central unit 10 includes power supply means 
11, power supply control means 12 and processing and control means 13. 30 
volt and 5 volt switched mode power supplies 14, 15 in the power supply 
means 11 are fed by the battery +V which is 12 volts in an automotive 
vehicle electrical system. So as to minimize current drain and conserve 
battery power, the system has a sleep mode in which the power supply means 
11 are turned off by the power supply control means 12, which are also fed 
by the battery +V, and an active mode in which the power supply means 11 
are turned on by the power supply control means 12. In the active mode of 
the system the power supplies 14, 15 operate a custom unit 16 and a 
microprocessor 17 connected thereto in the processing and control means 
13. Each low current signalling link 40 to a remote unit 20 has two data 
lines 41, 42 to each of which the processing and control means 13 applies 
an operation voltage in pulse form during the active mode of the system. 
Each data line 41 is a clock pulse line with the respective operation 
voltage in pulse form constituting clock pulses of 30 volts amplitude 
which are applied to that line 41 by a clock driver transistor TR1 under 
control of the custom unit 16 and which control the timing of the system 
time slot assignment multiplex. Each data line 42 is a signal line, and in 
each time slot a respective switch 18 in the custom unit 16 controls the 
application to that signal line 42 of zero volts or the fixed voltage 
supply of 30 volts via a pull-up resistor R1. 
In each remote unit 20, one of which is shown in FIG. 2, a 30 volt power 
supply 21 is derived from the clock pulses on the line 41 during the 
active mode of the system. A demultiplexing unit 22 has timing circuits 23 
responsive to the clock pulses on the line 41 and from which switches 24 
are operated to connect the signal line 42 of the low current signalling 
link through a corresponding demultiplexer channel in the appropriate time 
slot. Each remote unit 20 can connect for example sixteen channels, five 
of which are shown in FIG. 2. 
A variable resistor sensor 50 is shown wired to one of the channels in the 
remote unit 20. With the sensor 50 connected in the signal line 42 during 
the appropriate time slot and the switch 18 in the central unit 10 open 
during that time slot, then the voltage on the signal line 42 is an input 
signal from the sensor 50 due to its resistance, and this input signal is 
recognized via an analogue-to-digital converter 19 in the central unit 10. 
Two manually operable electrical toggle switches 60, 61 are shown each 
wired to a respective other one of the channels in the remote unit 20 via 
an R-C filter. With each switch 60, 61 connected in the signal line 42 
during its appropriate time slot and the switch 18 in the central unit 10 
open during that time slot, then the voltage on the signal line 42 due to 
the resistance between the two terminals of that switch 60, 61 is 
recognized via the analogue-to-digital converter 19 in the central unit 10 
as a respective first or second condition of a binary input signal from 
that switch 60, 61. 
Two other channels in the remote unit 20 are shown each connected in the 
remote unit to a respective output circuit 25. The state of the switch 18 
during the appropriate time slot will provide an output signal on the 
signal line 42 to power switching means 26 in the respective output 
circuit 25 to control a high current from the battery +V via a fuse 30 to 
a respective load, for example a lamp 70 or a starter switch solenoid 71, 
wired to the remote unit 20. The microprocessor 17 in the central unit 10 
ensures that the output signal on a signal line 42 to control a high 
current to a particular load 70, 71 connected to any one of the remote 
units 20 is in response to an input signal from a particular switch 60, 61 
which is to be associated with that load 70, 71 and is connected to any 
one of the remote units 20. 
The low currents in the low current signalling links of the system, for 
example through the signal line 42 when it includes one of the switches 
60, 61 may be, for example, not greater than 5 mA. The high currents 
through the loads of the system, for example to one of the loads 70, 71 
controlled in response to one of the switches 60, 61 may be, for example, 
up to 10 amps. 
The power supply control means 12 in the central unit 10 are shown 
connected to one of the clock pulse lines 41 and activation voltage drive 
means 80 are shown connected to that clock pulse line 41 in the remote 
unit 20. The activation voltage drive means 80 are fed by the battery +V 
and are connected in parallel to each of the switches 60, 61. When the 
system is in the sleep mode the activation voltage drive means can be 
enabled by operation of one of the switches 60, 61 so as to apply an 
activation voltage, substantially equal to the 12 volt battery voltage +V, 
to the clock pulse line 41. The power supply control means 12 is enable 
responsive to the 12 volt activation voltage so as to turn on the power 
supply means 11 and the activation voltage drive means 80 is disabled 
responsive to the 30 volt clock pulse voltage consequently applied to the 
clock pulse line 41 at the start of the active mode of the system. When 
the system is in the active mode the activation voltage drive means 80 are 
maintained disabled and the power supply control means 12 are maintained 
enabled responsive to the clock pulses on the line 41. The system reverts 
to the sleep mode when the power supply control means 12 are disabled 
responsive to discontinuation of the clock pulses on the line 41. The 
detailed constitution and operation of the power supply control means 12 
in the central unit 10 and the activation voltage drive means 80 in the 
remote unit 20 will be described below. 
The power supply control means 12 consists essentially of a comparator COM 
fed by the battery +V during both the sleep mode and the active mode of 
the system. The output of the comparator COM is connected to the switched 
mode power supply 14 of the power supply means 11 so as to turn on or turn 
off that power supply 14 and hence also the power supply 15. One input of 
the comparator COM, effectively an input of the power supply control means 
12, is connected to a capacitor C1, to a resistor R2 and, via an isolating 
diode D1, to the clock pulse line 41. The other input of the comparator 
COM is connected to a reference voltage +V1 which is derived directly from 
and has a value less than the 12 volt battery voltage +V. When the system 
is in the sleep mode the capacitor C1 is discharged and the output of the 
comparator COM maintains the power supply means 11 turned off. When the 
activation voltage of substantially 12 volts is applied to the line 41 by 
the activation voltage drive means 80 at the remote unit 20 the capacitor 
C1 is charged until it reaches a value above the reference voltage value 
+V1 whereupon the output of the comparator COM switches the system into 
the active mode by turning on the power supply means 11 to operate the 
control and processing means 13. The 30 volt clock pulse voltage applied 
to the line 41 by the clock driver transistor TR1 at the start of the 
active mode disables the activation voltage drive means 80 and hence the 
12 volt activation voltage is removed from the line 41. However, the R2C1 
time constant in relation to the duration of and intervals between the 30 
volt amplitude clock pulses on the line 41 during the active mode of the 
system is such that the capacitor C1 is maintained charged above the 
reference voltage value +V1 responsive to the clock pulses and the output 
of the comparator COM remains stable to keep the power supply means 11 
turned on. In order for the system to revert to the sleep mode it is 
simply necessary for the control and processing means 13 to discontinue 
application of the clock pulses to the lines 41 so that the capacitor C1 
discharges to below the reference voltage value +V1 whereupon the output 
of the comparator COM turns off the power supply means 11. 
The activation voltage drive means 80 in the remote unit 20 includes a 
p-n-p bipolar transistor TR2 having its emitter fed by the 12 volt battery 
+V, via a protective diode D2, during both the sleep mode and the active 
mode of the system. The collector of the transistor TR2 is connected to 
the clock pulse line 41. Two resistors R3, R4 are connected in series to 
the 12 volt battery +V. The two switches 60, 61 are connected in parallel 
via isolation diodes D3, D4 and the resistor R4 to the base of the 
transistor TR2. A capacitor C2 is connected across the resistor R3 to the 
base of the transistor TR2. When the system is in the sleep mode the 
capacitor C2 is discharged and the transistor TR2 is turned off. When one 
of the switches 60, 61 is operated the end of the resistor R4 connected to 
that switch is brought substantially to ground potential allowing base 
current to flow in the transistor TR2 which is thereby turned on to apply 
via its collector substantially +12 volts as the activation voltage to the 
clock pulse line 41. The R3C2 time constant in relation to the duration of 
the clock pulses on the line 41 is such when the + 30 volt clock pulse 
voltage is consequently applied to the line 41 at the start of the active 
mode of the system it exceeds the substantially +12 volt activation 
voltage for a time sufficient to charge the capacitor C2 via the 
transistor TR2 collector-base diode to a value such that the transistor 
TR2 is turned off. While the system is in the active mode the R3C2 time 
constant in relation to the intervals between the 30 volt clock pulses on 
the line 41 is such that the capacitor C2 is maintained charged above a 
value sufficient to maintain the transistor TR2 turned off. 
Once the system has been put into the active mode by operation of one of 
the switches 60, 61, as described above, then the operated condition of 
that switch 60, 61 is detected as a binary input signal by the processing 
and control means 13 in the central unit 10 via the signal line 42 in the 
appropriate time slot, and the microprocessor 17 ensures that in response 
to that input signal an output signal is provided on a line 42 to one of 
the remote units 20 to operate an associated load such as the load 70 or 
71. During the active mode of the system the diodes D3, D4 provide means 
for maintaining mutual isolation of the demultiplexer channels to which 
the switches 60, 61 are connected. 
Each of the switches 60, 61 may be termed a combined activation-function 
switch. That is to say that each switch 60, 61 is, by its connection to 
the activation voltage drive means 80, an activation switch by the 
operation of which the system may be brought into the active mode; and 
also each switch 60, 61 is, by its connection to one of the channels of 
the demultiplexing unit 22, a function switch whose binary input signal is 
recognized by the central unit 10 during the active mode of the system so 
as to indirectly operate an associated load connected to one of the remote 
units 20. Although it may be convenient to have more than one combined 
activation-function switch such as the switches 60, 61 connected in 
parallel to the activation voltage drive means 80 in the same remote unit 
20, it is possible to have only one such combined activation-function 
switch connected to the activation voltage drive means 80 in that remote 
unit 20. Furthermore it is possible to have a switch which is connected to 
the activation voltage drive means 80 in the remote unit 20 so as to be 
operable as an activation switch, but which is not connected to a 
demultiplexer channel in the remote unit 20 and so is not operable as a 
function switch. Such an activation switch may be a manually operable 
toggle switch, or it may be incorporated in a connector for equipment to 
operate the system in a test mode. 
The system may have activation voltage drive means 80 in only one of the 
remote units 20 with power supply control means 12 connected in the 
central unit 10 to the clock pulse line 41 in the signalling link 40 to 
that remote unit. However, activation voltage drive means 80 may be 
provided in more than one of the remote units 20 with corresponding power 
supply control means 12 connected in the central unit 10 to the clock 
pulse line 41 of each respective signalling link 40; in this case the 
outputs of the power supply control means 12 connected to the respective 
clock pulse lines 41 may be connected in parallel to the power supply 
means 11 and the system may be activated from any one of the remote units 
20 having an activation voltage drive means 80. 
Each remote unit 20 having activation voltage drive means 80 must be 
connected to the battery means +V, and each remote unit 20 having 
connected to it at least one load such as the load 70 or 71 must be 
connected to the battery means +V. There may be remote units 20 in the 
system which have only switches such as switches 60 or 61 and/or sensors 
such as sensor 50 connected to them and therefore strictly do not require 
to be connected to the battery means +V. However, in practice it will be 
convenient to provide a single cable to each remote unit which carries the 
signalling link 40 and also a battery connection wire; and this has the 
added advantage that a system may be modified by having a load connected 
to a hitherto unused channel at a remote unit. 
In the system described above with reference to FIG. 2 the battery means +V 
applies the same 12 volt battery voltage to the central unit 10 and to the 
remote units 20, the activation voltage is substantially the 12 volt 
battery voltage and the power supply means 11 converts the battery voltage 
into a higher voltage of 30 volts to be applied as the clock pulse 
voltage. In the application to an automotive vehicle electrical system 
there are noise immunity and other advantages provided by the 30 volt 
amplitude applied to the signalling lines 40. However, the particular 
circuit implementation of the activation voltage drive means 80 as 
described above relies essentially on the activation voltage being less 
than the clock pulse voltage so that after activation of the system the 
transistor TR2 is turned off by charging the capacitor C2 via the 
transistor collector-base diode. This circuit implementation would also 
work if, for example, the clock pulse voltage amplitude were 5 volts and a 
lower activation voltage of say 21/2 volts were derived from the battery 
at the remote unit 20. 
While the circuit implementation of the activation voltage drive means 80 
is particularly simple and reliable, it is envisaged that a logic circuit 
alternative could be provided which would respond to operation of an 
activation switch connected to the remote unit so as to apply an 
activation voltage to a data line in a signalling link to the central unit 
and then be disabled responsive to the operation voltage consequently 
applied by the central unit to that data line at the start of the active 
mode. In this case the activation voltage drive means could be maintained 
disabled other than in response to the pulse form operation voltage on the 
data line to which it is connected, and in this case the activation 
voltage need not be of smaller amplitude than that of the pulse form 
operation voltage although it must be significantly different from that 
operation voltage. 
Finally, it is envisaged that the use of an existing data line which 
conveys a pulse form operation voltage in normal active mode operation of 
the system also to convey a different amplitude activation voltage to 
bring the system out of its sleep mode can apply to battery operated star 
wired information handling and control systems in which that dual purpose 
data line is not necessarily a clock pulse line, and furthermore in which 
the system is not necessarily adapted for the remote indirect operation of 
loads as in an automotive vehicle electrical system.