MagTek SWIPE READERS WITH 3-TRACK - Manual (Page 15)

Section 3. Operation
9
POWER UP MESSAGE AND TIMEOUTS
Between 10 to 15 milliseconds (mS) after power up, the reader will assert DAV to indicate that
the start up message is ready to be sent over the SPI bus. This message is comprised of the text
“SPI MAGTEK” followed by the firmware part number, an ASCII line feed (0Ah), and a binary
zero (00h) termination character.
An example start up message appears below:
SPI MAGTEK 21088831C01<LF><00h>
If the Host does not respond to the DAV assertion between 400 to 600 mS (i.e. by transitioning
the SCL line), the reader will time out and the start up message will not be sent. Thus, to prevent
this timeout, the Host should respond within 400 mS after DAV is asserted high.
The timeout for successive data bits, in the start up message, is between 100 to 150 mS. To
ensure a timeout does not occur, the Host should transition the SCL line at least once every
100 mS. This would correspond to collection of a new data bit every 200 mS for a minimum data
rate of 5 bits/second. Data can be clocked out at a maximum rate of 100 Kbits/second.
If a timeout occurs, the remainder of the startup message will not be transmitted. After the start
up message is transmitted (or not transmitted in the event of a timeout), the reader will then await
a card swipe.