ST92124JCR9TC View Datasheet(PDF) - STMicroelectronics
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ST92124JCR9TC
STMicroelectronics
ST92124JCR9TC Datasheet PDF : 429 Pages
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ST92F124/F150/F250 - GENERAL DESCRIPTION
1.4 I/O PORTS
Port 0, Port 1 and Port 9[7:2] provide the external
memory interface. All the ports of the device can
be programmed as Input/Output or in Input mode,
compatible with TTL or CMOS levels (except
where Schmitt Trigger is present). Each bit can be
programmed individually (Refer to the I/O ports
chapter).
Internal Weak Pull-up
As shown in Table 3, not all input sections imple-
ment a Weak Pull-up. This means that the pull-up
must be connected externally when the pin is not
used or programmed as bidirectional.
TTL/CMOS Input
For all those port bits where no input schmitt trig-
ger is implemented, it is always possible to pro-
gram the input level as TTL or CMOS compatible
by programming the relevant PxC2.n control bit.
Refer I/O Ports Chapter to the section titled “Input/
Output Bit Configuration”.
Schmitt Trigger Input
Two different kinds of Schmitt Trigger circuitries
are implemented: Standard and High Hysteresis.
Standard Schmitt Trigger is widely used (see Ta-
ble 3), while the High Hysteresis Schmitt Trigger is
present on ports P4[7:6] and P6[5:4].
All inputs which can be used for detecting interrupt
events have been configured with a “Standard”
Schmitt Trigger, apart from the NMI pin which im-
plements the “High Hysteresis” version. In this
way, all interrupt lines are guaranteed as “edge
sensitive”.
Push-Pull/OD Output
The output buffer can be programmed as push-
pull or open-drain: attention must be paid to the
fact that the open-drain option corresponds only to
a disabling of P-channel MOS transistor of the
buffer itself: it is still present and physically con-
nected to the pin. Consequently it is not possible to
increase the output voltage on the pin over
VDD+0.3 Volt, to avoid direct junction biasing.
Pure Open-Drain Output
The user can increase the voltage on an I/O pin
over VDD+0.3 Volt where the P-channel MOS tran-
sistor is physically absent: this is allowed on all
“Pure Open Drain” pins. In this case, the push-pull
option is not available and any weak pull-up must
be implemented externally.
Table 3. I/O Port Characteristics
Input
Output
Port 0[7:0]
TTL/CMOS
Push-Pull/OD
Port 1[7:3]
Port 1[2:0]
TTL/CMOS
TTL/CMOS
Push-Pull/OD
Push-Pull/OD
Port 2[1:0]
Port 2[3:2]
Port 2[5:4]
Schmitt trigger
TTL/CMOS
Schmitt trigger
Push-Pull/OD
Pure OD
Push-Pull/OD
Port 2[7:6]
Port 3[2:0] 1)
Port 3.3
Port 3[7:4]
TTL/CMOS
Schmitt trigger
TTL/CMOS
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Port 4.0, Port 4.4
Schmitt trigger
Push-Pull/OD
Port 4.1
Port 4.2, Port 4.5
Port 4.3
Schmitt trigger
TTL/CMOS
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Push-Pull/OD
Port 4[7:6]
High hysteresis Schmitt trigger Pure OD
Port 5[2:0], Port 5[7:4] Schmitt trigger
Push-Pull/OD
Port 5.3
TTL/CMOS
Push-Pull/OD
Port 6[3:0]
Port 6[5:4]
Port 6[7:6] 1)
Schmitt trigger
Push-Pull/OD
High hysteresis Schmitt trigger Push-Pull/OD
Schmitt trigger
Push-Pull/OD
Port 7[7:0]
Schmitt trigger
Push-Pull/OD
Port 8[1:0]
Port 8[7:2]
Schmitt trigger
Schmitt trigger
Push-Pull/OD
Push-Pull/OD
Port 9[7:0]
Schmitt trigger
Push-Pull/OD
Legend: WPU = Weak Pull-Up, OD = Open Drain.
Weak Pull-Up
No
Yes
No
Yes
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Reset State
Bidirectional
Bidirectional WPU
Bidirectional
Input
Input CMOS
Input
Input CMOS
Input
Input CMOS
Input
Input
Bidirectional WPU
Input CMOS
Input
Input
Input
Input CMOS
Input
Input
Input
Input
Input
Bidirectional WPU
Bidirectional WPU
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