MPC52xx_PSC_BUFSIZE
#define MPC52xx_PSC_RFALARM (MPC52xx_PSC_BUFSIZE * 20 / 100)
unsigned send_at_once = MPC52xx_PSC_BUFSIZE;
if (t->len - rb > MPC52xx_PSC_BUFSIZE) {
rfalarm = MPC52xx_PSC_BUFSIZE - (t->len - rb);