SDA6000 Datasheet, PDF (99/380 Pages) Infineon Technologies AG – Teletext Decoder with Embedded 16-bit Controller

SDA 6000
Interrupt and Trap Functions
Increment Control Field INC controls, if one of the PEC pointers is incremented after
the PEC transfer. However, it is not possible to increment both pointers. If the pointers
are not modified (INC = ‘00’) the respective channel will always move data from the
same source to the same destination.
Note: The reserved combination ‘11’ is changed to ‘10’ by hardware. However, it is not
recommended to use this combination.
The PEC Transfer Count Field COUNT controls the action of a respective PEC channel,
where the content of bit field COUNT, at the time the request is activated, selects the
action. COUNT may allow a specified number of PEC transfers, unlimited transfers or
no PEC service at all.
The table below summarizes, how the COUNT field itself, the interrupt requests flag IR
and the PEC channel action depends on the previous content of COUNT.
Previous Modified IR after PEC Action of PEC Channel
COUNT COUNT service
and Comments
FF_H
FF_H
‘0’
Move a Byte / Word
Continuous transfer mode, i.e. COUNT is not
modified
FE_H … 02_H FD_H … 01_H ‘0’
01_H
00_H
‘1’
Move a Byte / Word and decrement COUNT
Move a Byte / Word
Leave request flag set, which triggers another
request
00_H
00_H
(‘1’)
No action!
Activate interrupt service routine rather than
PEC channel.
The PEC transfer counter allows the servicing of a specified number of requests by the
respective PEC channel, and then (when COUNT reaches 00_H) activates the interrupt
service routine, which is associated with the priority level. After each PEC transfer the
COUNT field is decremented and the request flag is cleared to indicate that the request
has been serviced.
Continuous transfers are selected by the value FF_H in bit field COUNT. In this case
COUNT is not modified and the respective PEC channel services any request until it is
disabled again.
When COUNT is decremented from 01_H to 00_H after a transfer the request flag is not
cleared, which generates another request from the same source. When COUNT already
contains the value 00_H, the respective PEC channel remains idle and the associated
interrupt service routine is activated instead. This provides a choice if a level 15 or 14
request is to be serviced by the PEC or by the interrupt service routine.
Users Manual
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2000-06-15