Vector Drive Complete Logic - Fluke 9100 Series Service Manual

VECTOR DRIVE COMPLETE LOGIC

There are two different mechanisms for controlling the completion of
vector driving, both of which are selected by the vector file in use.
The Vector Drive Complete circuitry consists of a 74AC02 NOR Gate (U20),
a 74ACT86 Exclusive OR Gate (U17), a 74ACT74 D Flip-flop (U16), and a
74AC08 AND Gate (U19).
Performing a General Stop
To stop the vector at a certain location within the vector file, a STOP
statement may be placed in the vector file. The DONEDRV line (U601-15)
goes high at the final vector address. DONEDRV is inverted by U20, which
produces the DONE- signal. DONE- does not allow the CLKMUX-OUT signal to
pass from U19-2 to U19-3. DONE- also clears U13 (which disables SSGATE-
by setting it high) to prevent further clocking of the RAM. DONE- is
also routed through J5-28 to J4-28 on the Main PCA to U25-16, where the
vector drive status is reflected in bit 3 of the Status Nybble.
Performing a Loop and Stop
To loop a specified number of times and then stop vector driving with no
further vectors being driven, a STOP statement may be placed after an
ENDLOOP statement in the vector file.
The LOOP-DONE signal is normally low. This signal remains low until the
final pass through the loop has begun. As long as LOOP-DONE is low, the
output of U16-9 is also low, preventing the BOTH signal from passing
through U19.
The LOOP signal is active one vector before the end of the loop to
permit address loading (since the module uses a pipeline scheme). The
BOTH signal is active at the same time as the final vector of the loop
is driven. Since U17 inverts BOTH, the current status of LOOP-DONE is
not latched until the first vector in the loop is driven (BOTH returns
low, clocking U16).
At the conclusion of the next-to-last pass through the loop, LOOP-DONE
is set high. On the last vector of the loop, BOTH goes high. When the
first vector of the loop is driven, BOTH returns low. The inversion of
BOTH latches LOOP-DONE, setting U16-9 high. As soon as the last vector
in the last pass through the loop is driven, BOTH returns high and
U19-6 goes high, generating the DONE- signal. From this point, the
signal is routed as described in the heading "Performing a General
Stop."
See the Loop Control Function Block for further information on how
looping operates.
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2/Theory of Operation