Functional Description
– processing of S commands
– flow control with RR/RNR
– response generation
– recognition of protocol errors
– transmission of S commands, if an acknowledgement is not received
– continuous status query of remote station after RNR has been received
– programmable timer/repeater functions.
The processing of frames in auto mode is described in detail in chapter 2.8.5: Documentation
of the Auto Mode.
2.8.3
Reception of Frames
A 2 × 32 byte FIFO buffer (receive pools) is provided in the receive direction.
The control of the data transfer between the CPU and the ISAC-S is handled via interrupts.
There are two different interrupt indications concerned with the reception of data:
– RPF (Receive Pool Full) interrupt, indicating that a 32-byte block of data can be read from
the RFIFO and the received message is not yet complete.
– RME (Receive Message End) interrupt, indicating that the reception of one message is
completed, i.e. either
● one message ≤ 32 bytes, or
● the last part of a message > 32 bytes
is stored in the RFIFO.
Depending on the message transfer mode the address and control fields of received frames
are processed and stored in the Receive FIFO or in special registers as depicted in figure 58.
The organization of the RFIFO is such that up to two short (≤ 32 bytes), successive messages,
with all additional information can be stored. The contents of the RFIFO would be, for example,
as shown in figure 57.
Semiconductor Group
110
INFINEON [ Infineon ]
