PEF20525 INFINEON [Infineon Technologies AG], PEF20525 Datasheet - Page 216

• Manufacturer Part Number: PEF20525
• Description: 2 Channel Serial Optimized Communication Controller for HDLC/PPP
• Manufacturer: INFINEON [Infineon Technologies AG]

If the transmit command does not include an end of message indication (CMDRL.XME),
SEROCCO-H will repeatedly request for the next data block by means of an ’XPR’
interrupt as soon as no more than 32 bytes are stored in the XFIFO, i.e. a 32-byte pool
is accessible to the CPU.
This process will be repeated until the CPU indicates the end of message per ’XME’
command, after which packet transmission is finished correctly by appending the CRC
and closing flag sequence. Consecutive packets may be transmitted as back-to-back
packets and may even share a flag (enabled via CCR1L.SFLG), if service of XFIFO is
quick enough.
In case no more data is available in the XFIFO prior to the arrival of the end-of-message
indiction (’XME’), the transmission of the packet is terminated with an abort sequence
and the CPU is notified per interrupt (ISR1.XDU, transmit data underrun). The packet
may also be aborted per software at any time (CMDRL.XRES).
The data transmission sequence, from the CPU’s point of view, is outlined in
Figure 53
Data Sheet
Transmit serial
data
Interrupt Driven Data Transmission (Flow Diagram)
Issue Command
CMDRL.XIF
CMDRL.XF
or
No
Reset Transmitter
(CMDRL.XRES)
End of Message
(up to 32 bytes)
'XPR' Interrupt
Write Data to
READY
START
XFIFO
XFIFO
216
?
Yes
CMDRL.XIF+.XME
CMDRL.XF+.XME
Issue Command
or
Transmit serial
append trailer
Action taken
by CPU
Interrupt
indication to CPU
Action taken
by the SCC
data and
Programming
PEB 20525
PEF 20525
Figure
2000-09-14
53.