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24
Serial Interface Connections
The serial interface on the MT Series can be connected to any device
capable of serial communication, including microcontrollers, RS-232 drivers
and computers. The figure below gives an example of connecting the MT
to the Linx QS Series USB module for connection to a computer.
The USB module follows the RS-232 convention of using separate lines
for data input and data output while the transcoder has a single line for all
data. This requires a switch to alternatively connect the transcoder’s SER_
IO line to the data lines on the module.
The RTS line is used to throw the switch as well as to activate the CRT/
LRN line placing the transcoder into Serial Mode. This gives the PC the
ability to control when communication is initiated.
The MODE_IND line will go high when the transcoder is prepared to send
data, so the CTS line on the USB module is used to monitor the MODE_
IND line. This allows the computer to know when to throw the switch and
look for data from the transcoder.
One point of note is that voltage translation may be necessary if the 5V
USB module is used to communicate with a transcoder operating at 3V.
There are many components and methods for implementing level shifting,
so it is up to the designer to determine the best solution for the product.
USBDP
USBDM
GND
DSR
DATA_IN
DATA_OUT
RTS
CTS
DTR
TX_IND
VCC
SUSP_IND
RX_IND
485_TX
RI
DCD
1
2
3
4
5
6
7
89
10
11
12
13
14
15
16
VCC
D6
D7
CRT/LRN
ENC_SEL
SER_IO
CONFIRM
TR_PDN
TR_SEL
TR_DATA
GND
D5
D4
D3
LATCH
SEL_BAUD
MODE_IND
D2
D1
D0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
LICAL-TRC-MT
SDM-USB-QS
8
7
6
5
1
2
3
4
V+
NC
GND
MAX4544
USB Type B
Connector
GND
5V
DAT -
DAT+
GND
GSHD
1
2
3
4
5
6
VCC
Figure 19: MT Series Transcoder Serial Interface to a PC
Figure 20: MT Series Transcoder Serial Interface Engine Command Set