SAB82538 Datasheet, PDF (70/253 Pages) Infineon Technologies AG – ICs for Communications

SAB 82538
SAF 82538
2.3.4.6 Continuous Transmission (DMA Mode only)
If data transfer from system memory to the ESCC8 is done by DMA (DMA bit in XBCH
set), the number of bytes to be transmitted is usually defined via the Transmit Byte Count
registers (XBCH, XBCL: bits XBC11…XBC0).
Setting the “Transmit Continuously” (XC) bit in XBCH, however, the byte count value is
ignored and the DMA interface of ESCC8 will continuously request for transmit data any
time 32 new bytes can be entered in XFIFO.
This feature can be used e.g. to transmit frames of length higher than the byte count
specified by XBCH, XBCL (frames with more than 4096 bytes).
Note: If the XC bit is reset during continuous transmission, the transmit byte count
becomes valid again, and the ESCC8 will request the amount of DMA transfers
programmed via XBC11..XBC0. Otherwise, the continuous transmission and the
generation of DMA requests is stopped when a data underrun condition occurs in
XFIFO. Instead of CRC, continuous “1”-s (IDLE) are transmitted thereafter.
2.3.4.7 Receive Length Check Feature
The ESCC8 offers the possibility to supervise the maximum length of received frames
and to terminate data reception in case this length is exceeded.
This feature is controlled via the special Receive Length Check Register (RLCR).
The function is enabled by setting the RC (Receive Check) bit in RLCR and
programming the maximum frame length via bits RL6…RL0. The maximum receive
length can be determined as a multiple of 32-byte blocks as follows:
MAX.LENGTH = (RL + 1) × 32
where RL is the value written to RL6…RL0.
All frames exceeding this length are treated as if they had been aborted by the remote
station, i.e. the CPU is informed via an
q RME interrupt, and the
q RAB bit in RSTA register is set.
To distinguish this from the case where an abort sequence is indeed received (sent by
the remote station), the receive byte count registers RBCH, RBCL will contain a value
exceeding the maximum receive length (via RL6...RL0) by one or two bytes.
Semiconductor Group
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