Atari 1040STE, Field Service Manual

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R0 low memory failed while setting up to run test.
R1 failed walking 1s or 0s.
R2 failed address (counting pattern).
R3 failed 64K boundary test. Probable failure in GSTMCU.
R4 failed while displaying area tested
(video RAM).
3.8 ROM TEST (O)
This test reads the configuration bytes of the operating system to determine the
version, language/country, and TV standard (PAL or NTSC). All bytes from operating
system ROMs are then read and the checksums and CRCs (cyclic redundancy
check) are calculated. The configuration byte is then read to determine the language
and version of the ROM. The correct checksum and CRC is then read from a
look-up table. The unit fails if the values found do not match the values from the
look-up table.
Incorrect checksums are indicated by a message. If an error is displayed, replace the
corresponding ROM.
New versions of TOS will not cause this test to fail since the calculated CRC is
compared with a value found in the new TOS ROMs and is independent of a fixed
look up table
.
3.9 COLOR TEST (C)
There are four screens in this selection. The first two are used to verify the color
circuitry, the third verifies the vertical scrolling circuit, and the fourth verifies
horizontal scrolling.
Screen One: red, green, blue, and white color bands are shown. Each band consists
of 16 levels of intensity. All 16 color palettes are represented, each palette is a
vertical strip across the screen (strips should not be discernible, but each color
should be a straight line across the screen). Because of the tight timing involved,
keystroke interrupts will cause the display to fitter.
Screen Two: This is the same as screen one except cyan, magenta, yellow, and
white color bands are shown. These colors are formed by adding together two
primary colors (blue + green, blue + red, red + green). The operator should see that
there are no gaps or missing scan lines in the display. If lines are missing, check the
three outputs on the Video Shifter for that color, and verify the values of the resistors
on the output. Too low a brightness setting on the monitor will cause the monitor not
to distinguish between fine levels, making it appear there are only four levels being
output.
The Video Shifter has four outputs for red (R0, R1, R2, R3), green (G0, G1, G2. G3)
and blue (B0, B 1, B2, B3). Each of these quadruples is summed together by a
resistor network to give 16 levels of intensity for each color, depending on which of
the outputs are on. The values of the resistors give different weight to each output.
The values of the resistor at R0 is twice that of R 1, which is twice that of R2, etc.
This allows us to get 16 equal steps on the summed outputs. For example, R0 on