Guard Time

Guard time is defined as the minimum delay between two consecutive character frames. The ISO 7816 specification defines both a Character Guard Time (CGT) and a Block Guard Time (BGT). In both T = 0 and T = 1 modes, CGT is defined as the minimum delay between the leading edges of the two consecutive characters in the same direction of transmission. Block Guard Time (BGT) for T = 1 mode only is defined as the minimum delay between the leading edges of the two consecutive characters in the opposite directions. The BGT has a standard fixed value of 22 ETUs.