ID Tech Spectrum IIa User Manual
Page 10
Appendix B
MAGNETIC OUTPUT SIGNAL DESCRIPTIONS AND TIMING
DIAGRAM
Magnetic Stripe Reader/Smart Card Reader
DATAx (DATA TRACK LEVEL SIGNAL): The level of this signal indicates the value of the
current bit being read. A LOW level data bit has a value of ONE. A HIGH level data bit has a value
of ZERO. The data level is true and stable while the CLK (clock) pulse is low and at both the
falling and raising edges. The data rate is proportional to the data density on the magnetic stripe
and the velocity of the media being swiped. Example: For data densities from 75 to 210 BPI, and
velocities from 5 to 60 IPS, the data rates can range from 375 to 13,650 bits per second.
NOTE: The subscript x is the track number. It may be 1,2, or 3.
CLKx (CLOCK TRACK SIGNAL): This signal is a negative pulse that is nominally 40 micro
seconds in duration. The falling edge indicates that the DATA output is valid and continues until
after the rising edge. The clock signal can be used as a clocking signal for a shift register, etc.
The clock pulse width can be set at the factory, and therefore it can be modifi ed if required.
MD (MEDIA DETECT PIN 22): This output is a media detect signal. Its normal level is HIGH and
goes LOW to indicate that magnetic media is detected. This signal is created from reading the
leading zero on an encoded card, and only goes LOW (it is normally high) after detecting a set
number of zeros. After recognizing a suffi cient number of zeros, the MD signal goes LOW and
stays LOW throughout the decoding process. After the last fl ux reversal is read from the media, it
goes back to HIGH. Media detect is used to signal the start and end of a media swipe. NOTE: No
data is output until MD goes low.
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Tb: Bit Width, Track1: Tb = 1/(Swipe Speed * 210).
Track2: Tb = 1/(Swipe Speed * 75).
Td: Clock Delay Time, 2 ms.
Tw: Clock Width, Typical: 32 ms.
Timing diagram showing the relationship of the MD,
DATA, and CLOCK signals in a typical magnetic
decoded track.
MD
DATAx
CLKx
Tw
Td
Tb
1 0 0 1