Specifications

Print Controller Design Guide for Information Security:
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21. CSS (Customer Support System) – MFP Models Only
Overview of CSS Operations
• The CSS control center sends a request for service-related information to the MFP across a
telecommunications line, which is then received by the LADP (line adapter telephony box). The
LADP then obtains the requested information via the CSS I/F and sends it back to the CSS control
center. The service-related information requested by the CSS control center includes data related
to external charge devices (e.g. serial number, counter values), as well as other data.
• If an abnormal condition is detected in the MFP, the MFP sends a command to the LADP via the
CSS I/F to inform the CSS control center of the condition. The LADP then contacts the CSS control
center via a telecommunications line and reports the information.
Data Flow
• The SCS module extracts the information requested by the LADP out of the pre-defined RAM
location, and then sends it to the LADP via the CSS I/F. When an abnormal condition is detected in
the MFP, the SCS module reports this information to the LADP via the CSS I/F.
Data Security Considerations
• For MFP products that support the CSS function, a single-chip microcontroller is used to control all
CSS-related communication, including protocol conversion and the destruction of any illegal data.
On the structural layout diagram, this chip is located at the CSS I/F. The actions that the MFP CPU
can perform are limited to three types of pre-defined commands: Read, Write and Execute. These
are the only commands that can pass through the CSS I/F, i.e. the only actions that the external
source (CSS control center) can instruct the MFP CPU to perform. Through these commands, the
MFP performs the same processing tasks as when receiving the commands from the operation
panel, making it impossible for the operator to execute external programs or freely read/write to a
memory area of their choosing.
• Through this filtering, the CSS I/F will destroy any command other than the three pre-defined
commands mentioned above. In addition, the firmware for the single-chip microcontroller is stored
in a Mask ROM, making it impossible for its contents to be overwritten.