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PDF ELM621 Data sheet ( Hoja de datos )
| Número de pieza | ELM621 | |
| Descripción | SERIAL THREE BIT PORT | |
| Fabricantes | ELM Electronics | |
| Logotipo |  |
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ELM621
Serial Three Bit Port
Description
The ELM621 is a serially controlled, three bit
parallel I/O port in an 8 pin package. The high level
of integration employed means that very few
external components are required in order to
construct a fully functional circuit with this IC.
The ELM621 offers several convenient features
that many users will appreciate. The provision of a
16 byte buffer allows commands to be chained and
executed sequentially with one key stroke. The
controllable pullup resistor on the bit 3 port pin is
particularly helpful when interfacing to mechanical
switches, while the ability to control character echo
reduces overhead while operating under computer
control. Naturally, individual as well as simultaneous
read, set, clear and toggle commands are also
supported.
All communications with this device are via a
standard 9600 baud RS232 connection, using AT
style commands. No special characters are required,
so that virtually any terminal program can be used
with the ELM621. More advanced users will be
interested in operating this device under computer
program control – simply a matter of writing to and
reading from the device.
Applications
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• Home automation monitoring and control
• Robotics
• Security monitoring
• IC programmers
Block Diagram
Features
• Low power CMOS design - typically 1mA
• High speed (9600 baud) RS232 communications
• Standard ASCII commands and responses
• 16 byte receive buffer
• Switchable pullup resistance
• Minimum of external components required
• External reset input
• High current drive outputs - up to 25 mA
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
B2 2
B1 3
reset 4
8 VSS
7 B3
6 Tx
5 Rx
VDD
Tx 6
Rx 5
RS232
Interface
reset 4
Command
Interpreter
VDD
Port
Control
7 B3
2 B2
3 B1
ELM621DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
1 of 6
1 page  
ELM621
AT Commands
The following lists the commands that the
ELM621 recognizes. These are collectively referred
to as ‘AT’ commands due to the fact that each line
must be preceeded by the letters ‘A’ and ‘T’.
All commands except reset (‘Z’) require two
characters to be complete. The first is a descriptive
letter, while the second is chosen from one of the
options shown within the square brackets, adjacent
to the letter.
As an example, the R or read command can be
followed by either a 1, 2, 3, or an A, so to read the
state of bit 2, the command ‘AT R2’ would be issued,
and AT RA will read all bits.
Device Control
E [ 1 | N ] - terminal echo on
Selecting either E1 or EN will cause all characters
sent to the ELM621 to be retransmitted (or echoed)
back to the controlling device.
E [ 0 | F ] - terminal echo off
Selecting either E0 or EF will stop the echoing of
characters back to the controlling device.
ID - show the device identification string
This command is used to display the type of device
connected and the ROM version.
Z - reset
This command is used to reset the ELM621 to the
power on state. All three port pins will be configured
as inputs, the pullup resistor will be off, the output
latches will be cleared, and terminal echo will be
on.
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Port Control
I [ 1 | 2 | 3 | A ] - set port bit to input
Individually selects one, or simultaneously selects
all pins to be inputs, turning off the respective
output driver if it were on.
O [ 1 | 2 | 3 | A ] - set port bit to output
Selects one or all pins to be outputs, enabling the
respective output drivers. If the pullup were on, and
O3 or OA were issued, then the pullup would be
temporarily disabled. Returning B3 to the input
state would restore the pullup resistance.
P [ 1 | N ] - turn the B3 pullup resistance on
Selecting either P1 or PN will enable the internal
30KΩ resistor from pin 7 to VDD.
P [ 0 | F ] - turn the B3 pullup resistance off
Selecting either P0 or PF will disable the internal
30KΩ resistor from pin 7 to VDD.
Bit Control
C [ 1 | 2 | 3 | A ] - clear the output bit
Individually clears (to logic 0 or VSS) either one or all
of the port bits. If the pin(s) are also selected to be
outputs, then the logic level will appear immediately
on the output.
S [ 1 | 2 | 3 | A ] - set the output bit
Individually sets (to logic 1 or VDD) either one or all
of the port bits. If the pin(s) are also selected to be
outputs, then the logic level will appear immediately
on the output.
T [ 1 | 2 | 3 | A ] - toggle the state of the output bit
Reverses (or toggles) the logic level of the selected
pin(s). As with C or S, the pin(s) must also be
selected as outputs for an external change to occur.
The toggle command is convenient for creating
pulses, or strobes, on pins. For example, if bit 3 is
configured as an output, and is at a low level,
issuing the command AT T3 T3 will cause pin 7
(B3) to momentarily go to a high level, then return
low. As the ELM621 is interpreter driven, the width
of the pulse will be related to the number of
characters that need be translated. Minimum width
(~60µsec) is obtained with ATT3T3.
R [ 1 | 2 | 3 | A ] - read the level of the port pin
Reads the voltage level at the selected pin(s) and
reports the measured logic level. For example, if pin
2 is at VDD (logic 1), then issuing AT R2 will result
in a response of B2=1.
ELM621DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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| PDF Descargar | [ Datasheet ELM621.PDF ] | |
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