Intel manual SA-1100 Developer’s Manual 11-165

Peripheral Control Module

11.12.6.7Telecom Transmit FIFO Underrun Status (TTU) (read/write, nonmaskable interrupt)

The telecom transmit FIFO underrun status bit (TTU) is set when the telecom transmit logic attempts to fetch data from the FIFO after it has been completely emptied. When an underrun occurs, the telecom transmit logic continuously transmits the last valid telecom value, which was transmitted before the underrun occurred. Once data is placed in the FIFO and it is transferred down to the bottom, the telecom transmit logic uses the new value within the FIFO for transmission. When the TTU bit is set, an interrupt request is made.

11.12.6.8Telecom Receive FIFO Overrun Status (TRO) (read/write, nonmaskable interrupt)

The telecom receive FIFO overrun status bit (TRO) is set when the telecom receive logic places data into the telecom receive FIFO after it has been completely filled. Each time a new piece of data is received, the set signal to the TRO status bit is asserted, and the newly received data is discarded. This process is repeated for each new piece of data received until at least one empty FIFO entry exists. When the TRO bit is set, an interrupt request is made.

11.12.6.9Audio Transmit FIFO Not Full Flag (ANF) (read-only, noninterruptible)

The audio transmit FIFO not full flag (ANF) is a read-only bit that is set whenever the audio transmit FIFO contains one or more entries that do not contain valid data and is cleared when the FIFO is completely full. This bit can be polled when using programmed I/O to fill the audio transmit FIFO over its halfway mark. This bit does not request an interrupt.

11.12.6.10Audio Receive FIFO Not Empty Flag (ANE) (read-only, noninterruptible)

The audio receive FIFO not empty flag (ANE) is a read-only bit that is set whenever the audio receive FIFO contains one or more entries of valid data and is cleared when it no longer contains any valid data. This bit can be polled when using programmed I/O to remove remaining bytes of data from the receive FIFO because DMA service and CPU interrupt requests are made only when four or more bytes reside within the FIFO (3, 2, or 1 bytes may remain at the end of a frame). This bit does not request an interrupt.

11.12.6.11Telecom Transmit FIFO Not Full Flag (TNF) (read-only, noninterruptible)

The telecom transmit FIFO not full flag (TNF) is a read-only bit that is set whenever the telecom transmit FIFO contains one or more entries that do not contain valid data and is cleared when the FIFO is completely full. This bit can be polled when using programmed I/O to fill the telecom transmit FIFO over its halfway mark. This bit does not request an interrupt.

SA-1100 Developer’s Manual 11-165