hd_sctrl
hd_sctrl(type | HD_WRITE | STROBE); /* set direction, address */
hd_sctrl(type | HD_WRITE); /* raise E */
hd_sctrl(type | HD_WRITE | STROBE); /* lower E */
hd_sctrl(type | HD_READ | STROBE); /* set direction, address */
hd_sctrl(type | HD_READ); /* raise E */
hd_sctrl(type | HD_READ | STROBE); /* lower E */
hd_sctrl(STROBE);