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NTE8212
Integrated Circuit
Schottky, 8–Bit Input/Output Port
Description:
The NTE8212 input/output port is an integrated circuit in a 24–Lead DIP type package and consists
of an 8–bit latch with three–state output buffers along with control and device selection logic. Also
included is a service request f lip–fl op f or t he c ontrol a nd g eneration o f i nterrupts t o t he m icroprocessor.
Features:
D Fully Parallel 8–Bit Data Register and Buffer
D Service Request Flip–Flop for Interrupt Generation
D Low Input Load Current: 0.25mA Max
D Three State Outputs
D Outputs Sink 15mA
D 3.65V Output High Voltge for Direct Interface to 8080A Processor
D Asynchronous Register Clear
D Replaces Buffers, Latches and Multiplexers in Microcomputer Systems
D Reduces System Package Count
Absolute Maximum Ratings: (TA = +25°C, Note 1 unless otherwise specified)
All Output or Supply Voltages –0.5V to +7V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
All Input Voltages –1.0V to +5.5V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Currents 125mA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Temperature Range 0° to +70°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage Temperature Range –65° to +150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Note 1. Stress above those listed under “Absolute Maximum Ratings” may cause permanent dam-
age to the device. This is a stress rating only and functional operation of the device at these
or any other conditions above those indicated in the operational sections of this specification
is not implied. Exposure to absolute maximum rating conditions for extended periods may
affect device reliability.
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Electrical Characteristics: (TA = 0° to +70°C, VCC = 5V ±5% unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Unit
DC Characteristics
Input Load Current
STB, DS
MD Input |IL2| – – –0.75 mA
DS1 Input |IL3| – – –1.0 mA
Input Leakage Current
STB, DS, CLR, DI1 – DI8 Inputs |IH1| VR = 5.25V – – 10 µA
MD Input |IH2| – – 30 µA
DS1 Input |IH3| – – 40 µA
, CLR, DI1 – DI8 Inputs |IL1| VF = 0.45V – – –0.25 mA
2
Input Forward Voltge Clamp V
Input “Low” V oltage V
Input “High” V oltage V
Output “Low” Voltage V
Output “High” V oltage V
IC = –5mA – – –1.0 V
C
IL
IH
OLIOL
OHIOH
= 15mA – – 0.48 V
= –1mA 3.65 – – V
– – 0.85 V
2.0 – – V
Short Circuit Output Current IO5 VO = 0V, VCC = 5V –15 – –75 mA
Output Leakage Current, High Impedance
I
VO = 0.45V/5.25V – – 20 µA
O
State (DO0 – DO8)
Power Supply Current I
CC
– – 130 mA
AC Characteritics
Pulse Width t
pw
Data to Output Delay t
Write Enable to Output Delay t
data Setup Time t
we
set
Data Hold Time t
Reset to Output Delay t
Set to Output Delay t
Output Enable/Disable Time (Note 2) te/t
Clear to Output Delay t
Input Pulse Amplitude = 2.5V,
Input Rise & Fall Times = 5ns,
pd
Between 1V and 2V
Between 1V and 2V
Measurement made
at 1.5V with 15mA and 30pF
Test Load
h
r
s
d
c
30 – – ns
– – 30 ns
– – 40 ns
15 – – ns
20 – – ns
– – 40 ns
– – 30 ns
– – 45 ns
– – 55 ns
Note 2. R1 = 300Ω/10KΩ; R2 = 600Ω/1KΩ
Capacitance: (TA = +25°C, VCC = 5V, V
Parameter Symbol Test Conditions Min Typ Max Unit
Input Capacitance C
Input Capacitance C
Output Capacitance C
IN
IN
OUT
= 2.5V, f = 1MHz, Note 3 unless otherwise specified)
BIAS
DS1, MD – – 12 pF
DS2, CLR, STB, DI1 – DI
DO1 – DO
8
8
Note 3. This parameter is periodically sampled and not 100% tested.
– – 9 pF
– – 12 pF
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Functional Description:
Data Latch
The 8 flip–flops that compose the data latch are of a “D” type design. The output (Q) of the flip–flop
follows the data input (D) while the clock input (C) is high. Latching occurs when the clock (C) returns
low.
The data latch is cleared by an asynchronous reset input (CLR
(NOTE: Clock (C) overrides Reset (CLR
Output Buffer
The outputs of the data latch (Q) are connected to three–state, non–inverting output buffers. These
buffers have a common control line (EN); enabling the buffer to transmit the data from the outputs of
the data latch (Q) or disabling the buffer, forcing the output into a high impedance state (three–state).
This high–impedance state allows the designer to connect the NTE8212 directly to the microprocessor bi–directional data bus.
Control Logic
The NTE8212 has four control inputs: DS1, DS2, MD and STB. These inputs are employed to control
device selection, data latching, output buffer state and the service request flip–flop.
DS1, DS2 (Device Select)
These two inputs are employed for device selection. When DS1 is low and DS2 is high (DS1 • DS2)
the device is selected. In the selected state the output buffer is enabled and the service request flip–
flop (SR) is asynchronously set.
).)
).
Service Request Flip–Flop (SR)
The (SR) flip–flop is employed to generate and control interrupts in microcomputer systems. It is asynchronously set by the CLR input (active low). When the (SR) flip–flop is set it is in the non–interrupting
state.
The output (Q) of the (SR) flip–flop is connected to an inverting input of a “NOR” gate. The other input
of the “NOR” gate is non–inverting and is connected to the device selection logic (DS1 • DS2). The
output of the “NOR” gate (INT ) is active low (interrupting state) for connection to active low input priority generating circuits.
MD (Mode)
This input is employed to control the state of the output buffer and to determine the source of the clock
(C) to the data latch.
When MD is in the output mode (high) the output buffers are enabled and the source of clock (C) to
the data latch is from the device selection logic (DS1 • DS2).
When MD is i n the input mode (low) the output buf fer state is determined by the device selection logic
(DS1 • DS2) and the source of clock (C) to the data latch is the STB (Strobe) input.
STB (Strobe)
STB is employed as the clock (C) to the data latch for the input mode (MD = 0) and to synchronously
reset the service request (SR) flip–flop.
Note that the SR flip–flop triggers on the negative edge of STB which overrides CLR.
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Pin Connection Diagram
DS
MD
DI
DO
DI
DO
DI
DO
DI
DO
STB
GND
1
1
2
3
1
4
1
5
2
6
2
7
3
8
3
9 16
4
10
4
11
12 13
24
23
22
21
20
19
18
17
15
14
V
CC
INT
DI
8
DO
DI
7
DO
DI
6
DO
DI
5
DO
CLR
DS
8
7
6
5
2
24 13
112
1.300 (33.02) Max .520
(13.2)
.225
(5.73)
Max
.100 (2.54)
.126
(3.22)
Min
.600 (15.24)1.100 (27.94)
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