Arria V Hard Processor System Technical Reference Manual

ID 683011
Date 12/02/2022
Public
Document Table of Contents

20.4.4.4. Master Microwire Serial Transfers

“National Semiconductor Microwire Protocol” describes the Microwire serial protocol in detail. †

Microwire serial transfers from the SPI serial master are controlled by the Microwire Control Register (MWCR). The MHS bit field enables and disables the Microwire handshaking interface. The MDD bit field controls the direction of the data frame (the control frame is always transmitted by the master and received by the slave). The MWMOD bit field defines whether the transfer is sequential or nonsequential. †

All Microwire transfers are started by the SPI serial master when there is at least one control word in the transmit FIFO buffer and a slave is enabled. When the SPI master transmits the data frame (MDD =1), the transfer is terminated by the shift logic when the transmit FIFO buffer is empty. When the SPI master receives the data frame (MDD = 1), the termination of the transfer depends on the setting of the MWMOD bit field. If the transfer is nonsequential (MWMOD = 0), it is terminated when the transmit FIFO buffer is empty after shifting in the data frame from the slave. When the transfer is sequential (MWMOD = 1), it is terminated by the shift logic when the number of data frames received is equal to the value in the CTRLR1 register plus one. †

When the handshaking interface on the SPI master is enabled (MHS =1), the status of the target slave is polled after transmission. Only when the slave reports a ready status does the SPI master complete the transfer and clear its BUSY status. If the transfer is continuous, the next control/data frame is not sent until the slave device returns a ready status. †