Sanma no Meitantei

Sanma no Meitantei
Developer: Namco Publisher: Namcot Platform: NES Released in JP: April 2, 1987 This game has hidden developer credits.

Sanma no Meitantei is a very light-hearted detective game starring Japanese comedian Sanma Akashiya.

Unused text

At offset 1C02E, this copyright text can be found:

COPYRIGHT 1986 NAMCO LTD.ALL RIGHTS RESERVEDMR TAKASI FUKAWA

Further down at 1FFC0 there's a string used as part of a CRC test routine mentioned below:

HARUHISA.UDAGAWA &  KUMI.HANAOKA

CRC Test

There are a series of Namco games, made by the same programmers Haruhisa Udagawa and Kumi Hanaoka, that contains the same self-test for the data integrity in (Babel no Tou, Dragon Buster, Family Jockey, Lupin Sansei: Pandora no Isan, Mappy-Land, Pro Yakyuu: Family Stadium, Sky Kid, Super Xevious: Gump no Nazo, Valkyrie no Bouken: Toki no Kagi Densetsu).

To enable any of these tests you need a special device that should be plugged into the expansion port. The operation of that device is very simple. It should accept the data bit from the data input port and return it back inverted to the output data port. The device consists of a 4-bit shift register, working as some sort of FIFO buffer. The input bits goes to the input and then shifted to be output after 4 cycles.

At the game's boot, it tries to send some special data to the device. If the data output doesn't match the data input inverted, then the game continues the normal operation. But if all data (usually 32, rarely 64 bytes) matches, self-tests will be performed. The program calculates 24-bit partial checksums for the PRG (excluding the last 8K) and the CHR data, summing only every 15th byte, and comparing it against the etalon.

Before testing of the PRG data, the background color turns red, before testing the CHR data, it turns green. If any of these tests have failed, the program will jump directly to the reset routine. It means one of these tests will be performed infinitely until the special device is unplugged, or until the test passes.

Normally, you'll see the red to green flash just before the game's boot. Or the static red screen if the PRG data is bad, or the flashing red to green screen if CHR data isn't good.

Using this Game Genie code GAVYNTEI, you can skip tests for the special device presense and jump straight to the integrity tests.

(Source: Cah4e3)