RCVDL56DPFL/SP, RCV56DPFL/SP, and RCV336DPFL/SP Designer’s Guide
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Table 3-1. Interface Memory Bit Definitions (Cont’d)
Mnemonic
Location
Default
Name/Description
FE
0Ah:4
0
Framing Error. When set, status bit FE indicates that more than 1 in 8 (or 1 in 4 for
extended overspeed) characters were received without a Stop bit in asynchronous
mode or an ABORT sequence was detected in SDLC/HDLC synchronous mode. When
reset, no framing error is detected.
In voice receive mode, FE = 1 and PE = 1 denote the first low byte.
FED
0Fh:6
–
Fast Energy Detector. When status bit FED is set, energy in the passband above the
selected receiver threshold has been detected (see RTH). DTR must be on in order for
FED to function in full duplex modes (DATA = 1).
FIFOEN
04h:4
0
FIFO Enable. When control bit FIFOEN = 1, the host can input up to 16 bytes of data
through TBUFFER, or voice samples through VBUFT, using the TDBE bit as a
software interrupt or the TXRQ signal (DMAE = 1) as a DMA request interrupt. In
HDLC, by default, if the host underruns the Transmit FIFO, the MDP will append a
CRC. If bit 3A5h: 6 is set, the MDP will instead abort the frame and provide an abort
code of 41h in ABCODE.
The Receive FIFO is always enabled. The host may wait up to 16 byte-times before
reading the data in RBUFFER. The RDBF bit or RXRQ signal (DMAE = 1) signals the
availability of receive data to the host. The trigger level for RDBF bit/RXRQ signal is
host programmable in DSP RAM. (See Section 4 for a detailed description about FIFO
operation.) (TPDM = 1)
FLAGDT
0Ah:6
–
V.21 Channel 2 Flag Detected. When set, status bit FLAGDT indicates that V.21
Channel 2 Flags (7Eh) are being detected. (V.33, V.17, V.29, V.27 ter)
FLAGS
0Ah:1
0
Flag Sequence. When set, status bit FLAGS indicates that the transmitter is sending
the Flag sequence in SDLC/HDLC mode, or a constant mark in parallel asynchronous
mode. When reset, FLAGS indicates that the transmitter is sending data.
GTE
03h:1
0
Guard Tone Enable. When set, control bit GTE causes the specified guard tone to be
transmitted (by the answering MDP only) according to the state of the GTS bit. (V.22
bis, V.22)
GTS
03h:0
0
Guard Tone Select. When set, control bit GTS selects the 550 Hz tone; when reset,
GTE selects the 1800 Hz tone. The selected guard tone will be transmitted only when
GTE is enabled. The host must set NEWC after changing the GTS bit. (V.22 bis, V.22)
HDLC
06h:4
0
HDLC Select. When control bit HDLC is set, HDLC operation is enabled. When HDLC
is reset, HDLC operation is disabled. The ASYN bit must be 0 and the TDBE bit must
be 1 prior to setting HDLC to a 1. The HDLC bit is valid only in synchronous parallel
data mode (ASYN = 0 and TPDM = 1). Not valid in FSK modes except V.21 channel 2.
RTS must be off before switching in or out of HDLC mode while in DATA mode.
HWRWK
15h:4
1
Host Write Wake up. When control bit HWRWK is set and the MDP is in sleep mode,
a host write to any register with the exception of 1Dh:7-0, will bring the MDP out of
sleep mode. (See SLEEP bit.)
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