MagTek SWIPE READERS WITH RS-232 - Manual (Page 14)

Swipe Readers with RS-232 IntelliHead
8
HALF-DUPLEX MODE
When operating in simplex mode (transmit only), the Reader is EIT/TIA-232 and V.28/V.24
compliant given the recommended operating conditions are met (see Specification table). While
simplex communication is sufficient for many applications, the Reader also has a limited
capability to receive transmissions from the host via the Reader’s RXD line. The Reader may be
disabled or enabled as outlined in the two sections below.
The Reader’s RXD line normally supplies the negative supply rail for the Reader’s transmit
output. Thus the Reader is half-duplex; it cannot transmit and receive signals simultaneously.
The RXD (Reader-referenced) line is only RS-232 compatible (not compliant) when used as an
input to the Reader. This is due to the high impedance of the line, 100 kΩ instead of the required
3 kΩ to 5 kΩ.
Also, the output of the Reader will reflect any signal received at its input. This “reflection” will
occur simultaneously with the transitions on the Reader’s input. The host must be expecting this
“reflection” and refrain from transmitting commands while the Reader is transmitting, otherwise
the data received by the host may be corrupted.
XON/XOFF
After a power-on, the Reader defaults to the XON state. In this state the Reader will transmit
card data immediately after a card swipe. When XOFF is received in the middle of transmitting
card data, the Reader will not halt transmission; the entire card data string will still be sent. After
completing the transmission if XOFF has been received, the Reader will capture the next card
swipe into its buffer; any subsequent swipes will now be ignored. When XON is received, the
Reader will transmit any captured data from its buffer. Note that it is possible that the captured
data may have one or more card data tracks containing errors. When in XOFF state, any
command will be ignored except for XON.
BAUD RATE
The communication rate is 9600 bps, 8-bit, no parity.
COMMAND SET (REV A FIRMWARE ONLY)
The Commands Set is as follows:
Command
Character Hex Comment
V 0x56 Retrieve Firmware Version, Reader will send the power-up string.
XON 0x11 see XON/XOFF description
XOFF 0x13 see XON/XOFF description