pef82902 Infineon Technologies Corporation, pef82902 Datasheet - Page 121

• Manufacturer Part Number: pef82902
• Description: 4b3t Second Generation Modular Isdn Nt Intelligent Extended
• Manufacturer: Infineon Technologies Corporation

PEF 81902
Functional Description
Possible Error Conditions during Transmission of Frames
If the transmitter sees an empty FIFO, i.e. if the microcontroller does not react quickly
enough to a XPR interrupt, a XDU (transmit data underrun) interrupt will be raised. If the
HDLC channel becomes unavailable during transmission the transmitter tries to repeat
the current frame as specified in the LAPD protocol. This is impossible after the first data
block has been sent (16 or 32 bytes), in this case a XMR transmit message repeat
interrupt is set and the microcontroller has to send the whole frame again.
Both XMR and XDU interrupts cause a reset of the XFIFO. The XFIFO is locked while a
XMR or XDU interrupt is pending, i.e. all write actions of the microcontroller will be
ignored as long as the microcontroller has not read the ISTAH register with the set XDU,
XMR interrupts.
If the microcontroller writes more data than allowed (16 or 32 bytes) , then the data in the
XFIFO will be corrupted and the STAR.XDOV bit is set. If this happens, the
microcontroller has to abort the transmission by CMDR.XRES and start new.
The general procedures for a data transmission sequence are outlined in the flow
diagram in
Figure
47.
Data Sheet
107
2001-11-12