7816_uart: add comment about f/d calculation

2012-05-18 08:41:08 +02:00 · 2012-05-18 08:41:08 +02:00 · 5aae62cb7b
parent f0fb308984
commit 5aae62cb7b
1 changed files with 2 additions and 0 deletions
--- a/firmware/src/simtrace/iso7816_uart.c
+++ b/firmware/src/simtrace/iso7816_uart.c
@ -157,6 +157,8 @@ static int compute_fidi_ratio(u_int8_t fi, u_int8_t di)
 	if (d == 0)
 		return -EINVAL;

+	/* See table 7 of ISO 7816-3: From 1000 on we divide by 1/d,
+	 * which equals a multiplication by d */
 	if (di < 8) 
 		ret = f / d;
 	else