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SINGLE-STEP AND PROGRAMMING
SINGLE-STEP
The UPI family has a single-step mode which allows
the user to manually step through his program one in-
struction at a time While stopped the address of the
next instruction to be fetched is available on PORT 1
and the lower 2 bits of PORT 2 The single-step feature
simplifies program debugging by allowing the user to
easily follow program execution
UPI-41A 41AH 42 42AH USER'S MANUAL
CHAPTER 4
POWER-DOWN MODES
Figure 4-1 illustrates a recommended circuit for single-
step operation while Figure 4-2 shows the timing rela-
tionship between the SYNC output and the SS input
During single-step operation PORT 1 and part of
PORT 2 are used to output address information In
order to retain the normal I O functions of PORTS 1
and 2 a separate latch can be used as shown in Figure
4-3
Figure 4-1 Single-Step Circuit
Figure 4-2 Single-Step Timing
231318 –28
231318 –29
53
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