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SAB 82532/SAF 82532
BISYNC Mode
Detailed Register Description
Semiconductor Group
202
07.96
Interrupt Controlled Data Transfer (interrupt mode)
Selected if DMA bit in XBCH is set to ‘0’.
Up to 32 bytes/16 words of received data can be read from the RFIFO following a RPF
or a TCD interrupt depending on the selected RFIFO mode (refer to RFC register):
RPF interrupt: A fixed number of bytes/words (programmed threshold level RFTH0, 1)
has to be read by the CPU.
TCD interrupt: Termination character detected. The received data stream is monitored
for a ‘termination character’ (programmable via register TCR). The number of valid bytes
in RFIFO is determined by reading the RBCL register.
If necessary, the CPU can have access to RFIFO by issuing RFIFO Read command
(CMDR.RFRD) before threshold level or termination character condition is reached. The
number of valid
bytes
is determined by reading the RBCL register. Additional
information: STAR:RFNE: RFIFO Not Empty.
DMA Controlled Data Transfer (DMA mode)
Selected if DMA bit in XBCH is set.
If the RFIFO contains the number of bytes/words defined by the threshold level, the
ESCC2 autonomously requests a block data transfer by DMA by activating the DRRn
line until the last valid data is read (the DRRn line remains active up to the beginning of
the last read cycle).
This forces the DMA controller to continuously perform bus cycles till all data is
transferred from the ESCC2 to the system memory (level triggered transfer mode of
DMA controller). If the end condition (TCD) is reached, the same procedure as above is
performed. DRRn is activated until the termination character is transferred, at which time
a TCD interrupt is generated. Generation of further DMA requests is blocked until TCD
interrupt has been acknowledged by issuing an RMC command. The valid
byte
count of
the last block can determined by reading the RBCL register following the TCD interrupt.
Note: Addresses within the 32-byte address space of the FIFO point all to the same
byte/word, i.e. current data can be accessed with any address within the valid
range.