C161U
Central Processor Unit
Preliminary Data Sheet
92
02.2000
PRELIMINARY
PRE
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M
INAR
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XC
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PT
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PEC Control Register Addresses
Byte/Word Transfer bit BWT controls, if a byte or a word is moved during a PEC service
cycle. This selection controls the transferred data size and the increment step for the
modified pointer.
Increment Control Field INC controls, if one of the PEC pointers is incremented after
the PEC transfer. It is not possible to increment both pointers, however. 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.
The PEC transfer counter allows to service a specified number of requests by the
respective PEC channel, and then (when COUNT reaches 00H) activate the interrupt
service routine, which is associated with the priority level. After each PEC transfer the
Register
Address
Reg. Space
Register
Address
Reg. Space
PECC0
FEC0
H / 60H
SFR
PECC4
FEC8
H / 64H
SFR
PECC1
FEC2
H / 61H
SFR
PECC5
FECA
H / 65H
SFR
PECC2
FEC4
H / 62H
SFR
PECC6
FECC
H / 66H
SFR
PECC3
FEC6
H / 63H
SFR
PECC7
FECE
H / 67H
SFR
Previous
COUNT
Modified
COUNT
IR after PEC
service
Action of PEC Channel
and Comments
FF
H
FF
H
‘0’
Move a Byte / Word
Continuous transfer mode, ie. COUNT is not modified
FE
H..02H
FD
H..01H
‘0’
Move a Byte / Word and decrement COUNT
01
H
00
H
‘1’
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.