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SA-1100 Developer’s Manual 11-123
Peripheral Control Module
11.10.10.6 Framing Error Status (FRE) (read/write, nonmaskable interrupt)
The framing error status (FRE) bit is set when a frame alignment error is detected by the receive
logic. A frame alignment error is detected on received data when a preamble is followed by
something other than another preamble or a start flag.
The following table shows the bit locations corresponding to the status and flag bits within HSSP
status register 0. Note that the reset state of all writable status bits is unknown (indicated by
question marks) and must be cleared (by writing a one to them) before enabling the HSSP. Also
note that writes to reserved bits are ignored and reads return zeros.
.
Address: 0h 8004 0074 HSSR0 Read/Write & Read-Only
Bit 76543210
Reserved FRE RFS TFS RAB TUR EIF
Reset00?00???
Bit Name Description
0EIF
End/error in FIFO (read-only).
0 – Bits 8–10 are not set within any of the eight bottom entries of the receive FIFO.
Receive FIFO DMA service requests are enabled.
1 – One or more tag bits (8 – 10) are set within one or more of the bottom eight entries of
the receive FIFO. Request interrupt, disable receive FIFO DMA service requests.
1TUR
Transmit FIFO underrun.
0 – Transmit FIFO has not experienced an underrun.
1 – Transmit logic attempted to fetch data from transmit FIFO while it was empty;
interrupt request signalled if not masked (if TUS=1).
2RAB
Receiver abort.
0 – No abort has been detected for the incoming frame.
1– Abort detected during receipt of incoming frame. Two or more chips containing no
pulses (0000) detected on receive pin. EOF bit set in receive FIFO next to last piece of
“good” data received before the abort, interrupt requested.
3 TFS
Transmit FIFO service request (read-only).
0 – Transmit FIFO is more than half-full (nine or more entries filled) or transmitter
disabled.
1 – Transmit FIFO is half-full or less (eight or fewer entries filled) and transmitter
operation is enabled. DMA service request signalled; interrupt request signalled if not
masked (if TIE=1).
4RFS
Receive FIFO service request (read-only).
0 – Receive FIFO contains 11 or fewer entries of data or receiver disabled.
1 – Receive FIFO is two- to three-fifths full (contains 9, 10, 11, or 12 entries of data) or
more, and receiver operation is enabled. DMA service request signalled; interrupt
request signalled if not masked (if RIE=1).
5FRE
Framing error.
0 – No framing errors encountered in the receipt of this data.
1 – Framing error occurred; preamble followed by something other than another
preamble or start flag, request interrupt.
7..6 — Reserved.