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SAFETY PRE AUTIONS
1
Use an isolation transformer for servicing.
2.
Maintain AC line voltage at rated input.
3.
Remove AC power from the computer before servicing or installing electrostatically sensitive devices. Examples of typical
ES devices are integrated circuits and semiconductor "chip" components.
4.
Use extreme caution when handling the printed circuit boards. Some semiconductor devices can be damaged easily by static
electricity. Drain off any electrostatic charge on your body by touching a known earth ground. Wear a commercially available
discharging wrist strap device. This should be removed prior to applying power to the unit under test.
5.
Use a grounded-tip, low voltage soldering iron.
6.
Use an isolation (times 10) probe on scope.
7.
Do not remove or install boards, floppy disk drives, printers, or other peripherals with computer AC power On.
8.
Do not use freon-propelled sprays. These can generate electrical charges sufficient to damage semiconductor devices.
9.
This computer is equipped with a grounded three-pronged AC plug. This plug must fit into a grounded AC power outlet. Do
not defeat the AC plug safety feature.
10. Periodically examine the AC power cord for damaged or cracked insulation.
11. The computer cabinet is equipped with vents to prevent heat build-up. Never block, cover, or obstruct these vents.
12. nstructions should be given, especially to children, that objects should not be dropped or pushed into the vents of the
cabinet. This could cause shock or equipment damage.
13. Never expose the computer to water. f exposed to water turn the unit Off. Do not place the computer near possible water
sources.
14. Never leave the computer unattended or plugged into the AC outlet for long periods of time. Remove AC plug from AC outlet
during lightning storms.
15. Do not allow anything to rest on AC power cord.
16. Unplug AC power cord from outlet before cleaning computer.
17. Never use liquids or aerosols directly on the computer. Spray on cloth and then apply to the computer cabinet. Make sure the
computer is disconnected from the AC power line.
LINE DEFINITIONS
A0ThruA15 ..................................................... Address Lines
A0D7 Thru A6D1 ............. Combined Address and Data Lines
A3B Thru A14B ................................. Buffered Address Lines
A15
RU ............. Communications Register Unit Address 15
AS .................................................. Column Address Strobe
DO Thru D15 ...................................... Converted Data Lines
RU
LK ...................... Communication Register Unit Clock
RU IN .................... Communication Register Unit Data nput
RU OUT ............. Communication Register Unit Data Output
SR .................... Chip Select Video Display Processor Read
SW ................... Chip Select Video Display Processor Write
DO Thru D7 ....................................... Bi-Directional Data Lines
DBIN ................................................................ Data Bus nput
DLY RST .......................................................... Delayed Reset
EXT INT ....................................................... External nterrupt
GROM
LK ............................................ Graphics ROM Clock
IAQHA ................................ nstruction Acquisition or Hold A
INT REQ ....................................................... nterrupt Request
LOAD ....................... CPU executes a Non-Maskable nterrupt
MBE ..................................................... Memory Block Enable
MB4 ......................................................... Memory Block Four
MEMEN .......................................................... Memory Enable
R/W ........................................................................ Read/Write
RAM BLK .......................................................... RAM Blanking
RAS ......................................................... Row Address Strobe
READY ......................................... Ready for Memory Access
RESET ................................. Reset Computer and Peripherals
ROMEN ............................................................... ROM Enable
RST 1 .............................................................................. Reset
SBE ...................................................... Speech Block Enable
SG
LK ................................. Central Processing Unit Clock
SND IN ................................................................... Audio nput
SNDOUT ........................................................... Audio Output
SPEE H .......................................... Speech Synthesizer nput
SYS RDY .......................................................... System Ready
VDP INT ............................. Video Display Processor nterrupt
WE ................................................................... Write Enable
01 .......................................................................... Phase One
02 .............................................
Phase Two
03 ........................................................................ Phase Three
04 .......................................................................... Phase Four
Any Bar above any alphabetical or numerical combination indicates line active in a low (0) state.
OMPUTERFA TS-OF-THE-MONTH SET NO.
F1 FOLDER
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