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22
Altera Corporation
MAX 7000B Programmable Logic Device Family Data Sheet
Preliminary Information
Programmable Pull-Up Resistor
Each MAX 7000B device I/ O pin provides an optional programmable
pull-up resistor during user mode. When this feature is enabled for an I/ O
pin, the pull-up resistor (typically 50 k
) weakly holds the output to
V
CCIO
level.
Bus Hold
Each MAX 7000B device I/ O pin provides an optional bus-hold feature.
When this feature is enabled for an I/ O pin, the bus-hold circuitry weakly
holds the signal at its last driven state. By holding the last driven state of
the pin until the next input signals is present, the bus-hold feature can
eliminate the need to add external pull-up or pull-down resistors to hold
a signal level when the bus is tri-stated. The bus-hold circuitry also pulls
undriven pins away from the input threshold voltage where noise can
cause unintended high-frequency switching. This feature can be selected
individually for each I/ O pin. The bus-hold output will drive no higher
than V
CCIO
to prevent overdriving signals.
The bus-hold circuitry weakly pulls the signal level to the last driven state
through a resistor with a nominal resistance (RBH) of approximately
8.5 k
.
Table 10
gives specific sustaining current that will be driven
through this resistor and overdrive current that will identify the next
driven input level. This information is provided for each VCCIO voltage
level.
The bus-hold circuitry is active only during user operation. At power-up,
the bus-hold circuit initializes its initial hold value as V
CC
approaches the
recommended operation conditions. When transitioning from ISP to User
Mode with bus hold enabled, the bus-hold circuit captures the value
present on the pin at the end of programming.
Table 10. Bus Hold Parameters
Parameter
Conditions
VCCIO Level
Units
1.8 V
2.5 V
3.3 V
Min
Max
Min
Max
Min
Max
Low sustaining current
High sustaining current
Low overdrive current
High overdrive current
V
IN
> V
IL
(max)
V
IN
< V
IH
(min)
0 V < V
IN
< V
CCIO
0 V < V
IN
< V
CCIO
30
–30
50
–50
70
–70
μ
A
μ
A
μ
A
μ
A
200
–295
300
–435
500
–680