pef20320 Infineon Technologies Corporation, pef20320 Datasheet - Page 194

• Manufacturer Part Number: pef20320
• Description: Multichannel Network Interface Controller For Hdlc With 32 Channels
• Manufacturer: Infineon Technologies Corporation

PEB 20320
Application Notes
Send Frame Routine
Calling ‘SendFrame’ after initialization of a channel results in executing ‘AddHdlcFrame’.
In that routine the transmit descriptors are disconnected from the message and linked to
the memory structures. If the message source is the ‘MROUTE Application Module’ the
hold bit and fe-bit indicating the end of a frame and the end of the list have already been
set/cleared in the MROUTE module, they are not modified anymore. If the message
source is any other module the fe-bit and hold bit are cleared in all descriptors except for
the last one. There the hold bit has to be set, to prevent the MUNICH32 from branching
to the next descriptor. Setting the fe-bit in the last descriptor only forces the MUNICH32
to send the data in one HDLC frame. The bits HI, V110 and CSM are cleared in both
cases.
Transmit/Receive Interrupt
A transmit acknowledge interrupt is treated by returning the transmit descriptor(s) to the
descriptor pool.
After a receive interrupt (FI bit set) the receive descriptors with c-bit set, are
disconnected from the list of receive descriptors, linked to a message and sent to the
MROUTE module. The next free receive descriptor in the list is linked to the memory
structures. An equivalent number of new descriptors is allocated and linked to the end of
the receive descriptor list.
5.2.3.2 Application Module MROUTE
The application module MROUTE implements the routing strategy.
Routing Strategy
Both devices the MUNICH32 and the LAN controller organize receive and transmit data
in a linked list of receive descriptors and a linked list of transmit descriptors. The data is
stored in data buffers of variable size. The receive/transmit descriptors contain the
address of the data buffer. The basic idea behind the routing strategy is, to take the
MUNlCH32’s receive descriptor and link it to the LAN controller’s transmit descriptor
queue. On the other hand to take the LAN controller’s receive descriptor and link it to the
MUNlCH32’s transmit descriptor queue.
User’s Manual
194
01.2000