Vector 4 - Page 164

| VECTOR 4
TECHNICAL INFORMATION
4.1 Automatic System Tests
4.7.1 Purpose Of Tests
The Vector 4 performs three automatic test programs at power-on and reset.
These test programs check out:
e - the ability of the RAM to retain data accurately.
® the system executive PROM for any checksum errors.
° the keyboard, to ensure that it is correctly attached and
functioning.
4.7.2 Memory Auto-test
This test first determines the top of memory (128K or 256K RAM). It then
tests each mappable 2K block of by a sequence of five read-write actions to
each memory location in the test block. The test uses data bytes of 00H,
0FFH, 055H, 0AAH, and a random value, '
If the RAM fails the test, the screen will display:
RAM MEMORY ERROR: BLOCK xx : EVEN/ODD ADDRESS : BITS IN
ERROR = xx *
* "gx" represents a two-digit hexadecimal number.
To determine which chip is faulty, check the block number. A bloeck number
between 00H and 03FH indicates an error in the lower 128K. A block number
between 040H and 07FH indicates an error in the upper 128K.
On the Vector 4 board, the RAM chips are arranged in two rows of eight
chips each. An odd address indicates a problem in the upper row; an even
address, the lower. Refer to Section 2.2-B of this manual for a detailed
explanation of how to isolate to the exact chip.
4.7.3 PROM Checksum Auto-test
The PROM checksum auto-test takes an eight-bit checksum of the SBC
Executive PROM and compares it to a known value. If the checksum is not
correct, the screen will display:
PROM CHECKSUM ERROR
09-01-82 7200-0001 III 4-9