MSR120D Programmer’s Manual UDN PM009 Rev. E
Section 3 -- Technical Specification 2005/2/23
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USB Connector Termination Assignment
Table 3-2. Connector Assignment
Contact
Number
Signal
Name
Typical Wiring
Assignment
1
Vbus
Red
2
D-
White
3
D+
Green
4 GND Black
Shell Shield Drain
Wire
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Communication
The interface receives and transmits serial bit stream at voltage levels compatible with the USB specification.
Transmission Protocol
The user may select from three different protocols: Protocol 0, 1, and 2.
Upon reset, the reader sends the power-on response “:”, depending upon the configuration setting. The reader then
configures itself to the protocol of the first command from the host. From this point on, the protocol is
unchangeable until a reset occurs.
Protocol 0
In Protocol 0, all characters are transmitted and received using exactly the characters listed in section 4. There are
no headers and Block Check Characters (BCC). Protocol 0 presumes no transmission errors. If the host detects an
error, it may request a retransmission.
Table 3-3. Example for Protocol 0
Host Command Reader Response
Comment
P
Ready
to
read
^
Reader
ACK
Protocol 1
In Protocol 1, all messages are preceded by the ASCII character <STX> and terminated with the ASCII character
<ETX>, followed by a one byte <BCC>. <BCC> is an XOR of the 7 data bits, excluding parity, of each character
in the entire message, including <STX>.
Format: <STX><MESSAGE><ETX><BCC>
where STX=02Hex and ETX=03Hex.
Table 3-4. Example for Protocol 1
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