DS785UM1
10-27
Copyright 2007 Cirrus Logic
DMA Controller
EP93xx User’s Guide
1
0
1
0
10
Current State:
Indicates the state that the Channel FSM is currently in:
00 - IDLE
01 - STALL
10 - ON
11 - NEXT
NextBuffer:
Informs the NFB service routine, after a NFB interrupt,
which pair of BASEx/MAXCOUNTx registers is free for
update.
0 - Update MAXCNT0/BASE0
1 - Update MAXCNT1/BASE1
The NextBuffer bit gets set to “1” when a write occurs to
BASE0 and it gets set to “0” when a write occurs to
BASE1. This bit alone cannot be used to determine which
of the two buffers is currently being transferred to. For
example, if BASE0 is written to, then NextBuffer gets set
to “1” and transfers will occur using buffer0. If, during this
transfer BASE1 gets written to, then NextBuffer gets set to
“0”, but the current transfer will continue using buffer0 until
it terminates. Then the DMA switches over to using
buffer1, at which time the NFB interrupt is generated and
software reads the NextBuffer status bit to determine what
buffer descriptor is now free for update. In this case it is
buffer0.
The NextBuffer status bit can be used in conjunction with
the CurrentState status bits to determine the active buffer.
If CurrentState = DMA_ON and NextBuffer = 1 then
Buffer0 is the active buffer.
If CurrentState = DMA_ON and NextBuffer = 0 then
Buffer1 is the active buffer.
If CurrentState = DMA_NEXT and NextBuffer = 0 then
Buffer0 is the active buffer.
If CurrentState = DMA_NEXT and NextBuffer =1 then
Buffer1 is the active buffer.
Summary of Contents for EP93 Series
Page 28: ...P 6 DS785UM1 Copyright 2007 Cirrus Logic Preface EP93xx User s Guide PP P ...
Page 162: ...5 36 DS785UM1 Copyright 2007 Cirrus Logic System Controller EP93xx User s Guide 55 5 ...
Page 576: ...15 18 DS785UM1 Copyright 2007 Cirrus Logic UART2 EP93xx User s Guide 1515 15 ...
Page 634: ...17 38 DS785UM1 Copyright 2007 Cirrus Logic IrDA EP93xx User s Guide 1717 17 ...
Page 648: ...19 6 DS785UM1 Copyright 2007 Cirrus Logic Watchdog Timer EP93xx User s Guide 1919 19 ...
Page 688: ...21 32 DS785UM1 Copyright 2007 Cirrus Logic I2S Controller EP93xx User s Guide 2121 21 ...
Page 790: ...27 20 DS785UM1 Copyright 2007 Cirrus Logic IDE Interface EP93xx User s Guide 2727 27 ...
Page 808: ...28 18 DS785UM1 Copyright 2007 Cirrus Logic GPIO Interface EP93xx User s Guide 2828 28 ...