MAX6900_CMD_READ
cmdbuf[0] = MAX6900_REG_RAM(a) | MAX6900_CMD_READ;
cmdbuf[0] = max6900_rtc_offset[i] | MAX6900_CMD_READ;
cmdbuf[0] = MAX6900_REG_SECOND | MAX6900_CMD_READ;
cmdbuf[0] = MAX6900_REG_SECOND | MAX6900_CMD_READ;