What Is Doctor Program? - JVC GR-DVA10 Technical Manual

4.1 WHAT IS DOCTOR PROGRAM?

The function and performance of a product (an electric/electronic appliance in this case) generally
depends on the program of the internal microcomputer. If there is some fault in the electrical function and
performance of a product, the program of its microcomputer should be changed (upgraded) at the
expenses of the manufacturer. To prepare for an unexpected trouble, recently manufactured articles store
a part of the program data in the EEPROM coupled with the microcomputer so that the program of the
microcomputer can be easily revised. Such the program data written in the EEPROM coupled with the
microcomputer is called the "Doctor Program".
If the microcomputer of an article has no need of support of the Doctor Program, no program data is
written in the EEPROM. Even in such the case, the EEPROM of recent products prepares specific
addresses (several bytes to dozens of bytes) as the area to write the Doctor Program. The area
(addresses) differs from model to model. Since the Doctor Program must vary depending on the program
of the microcomputer and expected troubles, its matching with the microcomputer (program) is very
important.
4.1.1 Matching of Doctor Program with Microcomputer Program
The program of the microcomputer can be revised by rewriting the Doctor Program stored in the EEPROM
coupled with the microcomputer. However, if the program of the microcomputer is changed by upgrading
or so, the Doctor Program conforming to the previous program stored in the EEPROM is useless. If the
microcomputer that is consistent with the Doctor Program stored in the EEPROM is replaced with a new
microcomputer of an upgraded one, continuous use of the Doctor Program to cope with a trouble may
develop an unexpected situation. An example of progress of revisions (upgrading) of the microcomputer
program and EEPROM Doctor Program is shown below.
Microcomputer A
No Doctor
P r o g r a m
If there is such the change in production of a series of products, matching of the microcomputer and
Doctor Program with each other is as follows.
Microcomputer A + No Doctor Program, Doctor Program A, or Doctor Program B = OK,
Microcomputer B + No Doctor Program or Doctor Program C = OK,
Microcomputer A + Doctor Program C = NG,
Microcomputer B + Doctor Program A or Doctor Program B = NG.
If the Doctor Program mismatches the microcomputer program, the product falls into troubles showing
various symptoms when the Doctor Program is rewritten and it is difficult to specify the cause of the
trouble, for example, the product fails in power supply or shows the picture abnormally depending on the
situation. Such being the case, pay careful attention to matching of the Doctor Program with the
microcomputer program (version).
SECTION 4
DOCTOR SYSTEM
Doctor Doctor
P r o g r a m A P r o g r a m B
Fig. 4-1-1 Example of progress of revisions
Microcomputer B
No Doctor
P r o g r a m
4-1
Doctor
P r o g r a m B