624
6 Reverse Engineering of Microcircuits
based on microcircuits, transistors, or specialized power control microcircuits. The
disadvantage of this approach is the need to use a great number of microcircuits and
discrete devices required for implementation of both tracking circuits registering
the moments of activation or short-term disappearance of supply voltage and for
circuits setting the electronic system in the initial state. Introduction of additional
ICs increases dimensions and power consumption and reduces general reliability of
the electronic system.
This section presents the results of development of an original circuitry-based
method of countering fault states occurring during disturbance of bipolar LSICs. This
method is based on using special logic devices referred to by the author (A. I. Belous)
as power control circuits. The main requirement for PCS is identification (detection)
of power-on moments, as well as faults (power-offs) of the programmed duration;
at the same time, PCS constantly monitors the condition of the power supply of the
microprocessor system during operation, since most of LSIC outputs after a fault
situation are detected at the moments of power supply mode interruption. Simplified
structure of such PCS and timing diagrams of its operation are shown in Fig. 6.97a,
b. Such a circuit was first implemented as a part of LSIC of the microprogram control
block.
Here, the author used the feature of most injection LSIC MPs—availability of two
mode outputs of the package used for connection to the positive output of a power
source. This feature served as a basis for organizing power control circuits embedded
in the LSIC. The essence of the developed method consists in the following.
A special logic block inside LSIC MP analyzing voltages at two positive pins of
its power supply allows for identification of pins with power supplied to only one
of the pins. Such situations should be compared with the concepts of “failure” or
“power-on.” In this case, due to presence of two potential power outputs of the LSIC
that are not connected to each other, it is possible to identify one of the two following
situations:
(a) Power-on method;
(b) Short-term disappearance of supply voltage. The additional extremely significant requirement for PCS is the necessity to ensure its workability in case of
presence of power at least at one of the outputs.
The PCS (Fig. 6.97a) includes
– Two triggers (T01 and T02) designed to generate and send signals of initial
settings (S1 and S2) corresponding to various situations associated with the
absence of power at inputs of E
1
p or E
2
p to other logic blocks of the LSIC
from PCS;
– The circuit implementing logical conjunction function from voltages at LSIC
power inputs (&
E );
– The decoder indicating that the effects of signals of S1 and S2 on logic blocks
of the LSIC ensured setting the LSIC in the required state;
– The m-bit counter providing the necessary LSIC delay in the initial state for
2 W clock cycles of the synchronization impulse.
6 Reverse Engineering of Microcircuits
based on microcircuits, transistors, or specialized power control microcircuits. The
disadvantage of this approach is the need to use a great number of microcircuits and
discrete devices required for implementation of both tracking circuits registering
the moments of activation or short-term disappearance of supply voltage and for
circuits setting the electronic system in the initial state. Introduction of additional
ICs increases dimensions and power consumption and reduces general reliability of
the electronic system.
This section presents the results of development of an original circuitry-based
method of countering fault states occurring during disturbance of bipolar LSICs. This
method is based on using special logic devices referred to by the author (A. I. Belous)
as power control circuits. The main requirement for PCS is identification (detection)
of power-on moments, as well as faults (power-offs) of the programmed duration;
at the same time, PCS constantly monitors the condition of the power supply of the
microprocessor system during operation, since most of LSIC outputs after a fault
situation are detected at the moments of power supply mode interruption. Simplified
structure of such PCS and timing diagrams of its operation are shown in Fig. 6.97a,
b. Such a circuit was first implemented as a part of LSIC of the microprogram control
block.
Here, the author used the feature of most injection LSIC MPs—availability of two
mode outputs of the package used for connection to the positive output of a power
source. This feature served as a basis for organizing power control circuits embedded
in the LSIC. The essence of the developed method consists in the following.
A special logic block inside LSIC MP analyzing voltages at two positive pins of
its power supply allows for identification of pins with power supplied to only one
of the pins. Such situations should be compared with the concepts of “failure” or
“power-on.” In this case, due to presence of two potential power outputs of the LSIC
that are not connected to each other, it is possible to identify one of the two following
situations:
(a) Power-on method;
(b) Short-term disappearance of supply voltage. The additional extremely significant requirement for PCS is the necessity to ensure its workability in case of
presence of power at least at one of the outputs.
The PCS (Fig. 6.97a) includes
– Two triggers (T01 and T02) designed to generate and send signals of initial
settings (S1 and S2) corresponding to various situations associated with the
absence of power at inputs of E
1
p or E
2
p to other logic blocks of the LSIC
from PCS;
– The circuit implementing logical conjunction function from voltages at LSIC
power inputs (&
E );
– The decoder indicating that the effects of signals of S1 and S2 on logic blocks
of the LSIC ensured setting the LSIC in the required state;
– The m-bit counter providing the necessary LSIC delay in the initial state for
2 W clock cycles of the synchronization impulse.