User's Manual

NBS Payment Solutions 35/55 User Manual
2.3.2 Operating system (OS) characteristics
The OS is (down)loaded into the memory. It is upgradeable. After a few fractions of a second following
powering up, it takes control. It checks the presence, integrity and authenticity of the system components
and application software present in the terminal.
The maintenance subsystem takes control in the following cases:
- if no authentic software application is present,
- or if a manual action by the operator is made when powering up,
- or if it is activated by application software.
The maintenance subsystem ensures, among other things, application software downloading.
The OS ensures the start of the multitask core and then runs the application software by making a set
of services available to them:
- Multitask management: Availability of a pre-emptive real-time environment, based on
interruptions, events and letter boxes. This management enables simultaneous
processing, which improves the terminal's performance.
- Input/output management: This is carried out under interruptions, generally in buffered
mode. Thus, the applications software developer enters a "conventional" C context.
- System alarms management: Certain incidents (e.g. swipe card reading error) detected by
the OS are recorded. They can be used later by the maintenance subsystem during remote
or local diagnostics.
- Application software alarms management: A number of incidents detected by the
software applications can be saved by the OS at their request. This recording is used later
as in the case of system alarms.
- Application software isolation management: The OS provides the mechanisms described
in the section on software isolation and memory protection. Between software isolation is
managed by an MMU (Memory Management Unit).
- Software loading and downloading management: The OS offers the (down)loading
services described in the section "Software loading"