3—Insert an MC68705P3, P5, R3, R5, U3 or U5 into the appropriate 28 or 40 pin socket. Again,
be sure that pin 1 of the part is at the end indicated by the silver dot. You can only program 1
MPU at a time. Be sure there is no other chip other than the one MPU and the 2732 (or 2764) in
the programmer at one time. The other socket should be empty. Make sure that you close the
handles on the Textool zif (green) sockets.
4—Press the button. The busy light should come on, indicating that the unit has applied power to
the programming sockets. Do Not Remove or Insert parts while the busy light is on! If the busy
light does not come on and stay on, it indicates that the 68705 may have a problem. Maybe you
forgot to close the handles on the Textool sockets.
5—After approximately 1.5 minutes (28 pin P3 or P5 MPU’s) or 3.0 minutes (40 pin R3, U3, R5 or
U5 MPU’s), the “Programmed”light should come on followed shortly (a few seconds) by the
“Verified”light. The program light indicates the completion of the program cycle. The verify light
indicates that the part was compared with the code in the 2732 (or 2764) and it compared
perfectly. The “busy”light will go out by itself at the end of the cycle.
6—After removing the MPU chip, press the program button to turn off the “program”and “verified”
lights. This is a desirable procedure to follow, so that there will not be any question as to whether
you had “already pressed the button”the next time you want to program an MPU.
III
Calibration
The model 705 programmer uses a crystal timebase and the programming voltage is temperature
compensated. It should therefore require no calibration. You may, from time to time, wish to
measure the Vpp voltage on the programming pin of a 68705 while it is programming. It should be
21 volts + or —.25 volts. This voltage may be adjusted by the trim pot inside the unit.
On newer Model 705 programmers there is another pot. It’s used to trim the VCC voltage on the
unit. The new Vcc adjust pot is the one closest to the bridge rectifier and 7805 voltage regulator.
While a chip is programming in the 28 or 40 pin socket adjust this pot so that there is
approximately 5.00 volts on the Vcc pin of the chip that is programming. This voltage can vary by
+ or —.25 volts, but the closer to 5.00 volts on the Vcc pin of the chip, the better.
