Testing Ram Chips  2114
for your Ms Pacman video game
Computer Aided Testing System

	System Description
	Ms Pacman Repair
	Other Test Examples
	Test Table
	Test Procedure
	Repair Blog
	Index of Links
	Other PCB's tested

This is a typical view while testing the ram chips on a Pacman-type PCB. In this example, the 2114 memory chips at locations 4K and 4N are being written to with random numbers between 0 and 255 for the master data value.       Ram chips 4K and and 4N operated together provide the 8-bit data values in the address range Hex 4000 to Hex 43FF in the Pacman memory map. The Ram chip at location 4K handles the lower 4-bits, (d0 - d3), while the Ram chip at location 4N handles the higher 4 bits (d4 - d7).        The basic events which occur in this test example are: generate 3FF (1024) random numbers, write the numbers to address range 4000-43FF, read back address range 4000 43FF, compare master data with read back data.         These tests are performed during the Ms Pacman test procedure which all boards undergo, when they are submitted for repair. Different groups of tests requests from the Pacman Test Table allow for testing of the Ram chips using different sets of numbers for the test.       This example also shows the sequence of events as they occur, during the processing of the test request, this is useful in proving that the test is being decoded and executed as expected.

Troubleshooting this area of the circuit:

		If it known that the RAM chips are good, however errors are received, then it is possible one of the support chips for this circuit may be at fault. Special software has been written in order to effectively diagnose individual address lines by pointing and clicking the pictures of pins on these chips, as this screen shows
By monitoring the pins on the board with an oscilloscope, these signals can be traced individually.  for example, by pointing at pin 15 on the 2114 label, this would cause only pin 15 to be "high" while all of the other address inputs to go "low".

Contact me at greg@gls1electronics.com  for more information about RAM failures on a Pacman board, or if you need your Pacman or Ms Pacman PCB repaired.