Mfp Interface Circuit Descriptions - Watkins-Johnson Company WJ-8718A/MFP Instruction Supplement

WJ-8718A/MFP
FIGURE 3-4
rising clock edge) and remain high until U17 resets or until the direction of rotation changes. If
the direction is counterclockwise, the D2 input is low each time the U17 clock transitions high;
Q2 will either be low from the time of U17 reset and will remain low, or will be high from
clockwise rotation and will go low at the first rising clock edge.
The sequence of the microprocessor program is such that following a RD of U17,
the processor addresses 1048 and U19Y4 goes low. This low level is inverted by U15D and clear
goes high, resetting the Ql and Q2 outputs to a low level. The reset procedure ensures that a
high level on Ql indicates that the tuning wheel has been rotated since the last time Q1 was
examined and, furthermore, because only 5 milliseconds has elapsed, the tuning wheel is still
being rotated and the microprocessor can proceed to increment or decrement the displayed
frequency. .
--,
I
DIR --'--~
I
ClK __
.J
I
UI7 02 __
.1
--,
I
UI7 ClK ---
I I I
02 (HI)
I
I
I
I I
I
Dl(HI),
I
r-
I
I
I
01 (HI)
J
I
~
I I
I
Figure 3-4. Timing Diagram For Tuning Wheel Clockwise Rotation
3.2
MFP INTERFACE CIRCUIT DESCRIPTIONS
The interface section of the MFP Option consists of two circuit boards, which
contain an Intel 8085A Microprocessor with memory, read-only, and write-only devices to
support the microprocessor.
. The
disc~ssions
in paragraphs 3.2.1 through 3.2.3.5 concern the microprocessor and
the functIOnal
~reas
dIrectly related to the microprocessor. Detailed circuit descriptions of the
IF and SynthesIzer Interface/Memory Boards (MFP-A3 and A4) follow, in paragraphs 3.2.4 and
3.2.5.
3-19