ATF2500C_08 ATMEL [ATMEL Corporation], ATF2500C_08 Datasheet - Page 5

• Manufacturer Part Number: ATF2500C_08
• Description: ATF2500C CPLD Family Datasheet
• Manufacturer: ATMEL [ATMEL Corporation]

5. Preload and Observability of Registered Outputs
0777K–PLD–1/24/08
The ATF2500Cs registers are provided with circuitry to allow loading of each register asynchro-
nously with either a high or a low. This feature will simplify testing since any state can be forced
into the registers to control test sequencing. A V
priate register high; a V
settings.
The PRELOAD state is entered by placing an 10.25V to 10.75V signal on SMP lead 42. When
the preload clock SMP lead 23 is pulsed high, the data on the I/O pins is placed into the 12 reg-
isters chosen by the Q select and even/odd select pins.
Register 2 observability mode is entered by placing an 10.25V to 10.75V signal on pin/lead 2. In
this mode, the contents of the buried register bank will appear on the associated outputs when
the OE control signals are active.
Figure 5-1.
Table 5-1.
Level Forced on Odd
PRELOAD Cycle
I/O Pin during
V
V
V
V
IH
IH
IH
IH
/V
/V
/V
/V
IL
IL
IL
IL
Preload Waveforms
Preload Levels
IL
Pin State
Q Select
will force it low, independent of the polarity or other configuration bit
High
High
Low
Low
Even/Odd
Select
High
High
Low
Low
IH
State after
High/Low
Even Q1
level on the odd I/O pins will force the appro-
Cycle
X
X
X
State after
High/Low
Even Q2
Cycle
X
X
X
State after
High/Low
Odd Q1
Cycle
ATF2500C
X
X
X
State after
High/Low
Odd Q2
Cycle
X
X
X
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