Data can be safely written, that is, tx_enain asserted, when tx_rdyout is asserted. After tx_rdyout is negated, additional writes using tx_enain can be safely performed provided tx_ovfout is never asserted. When tx_rdyout is asserted again, additional data can be written. If at any time the back-pressure mechanism is violated, the tx_ovfout is asserted to indicate the violation. Up to four write cycles might be safely performed after tx_rdyout is negated, but no more until tx_rdyout is asserted again.