Inserting A Tcb In An Active Chain - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

IOP/Core Interaction Options
Listing 7-1. Chain Assignment
R0=0;
dm(CPx)=R0;
R2=(TCB1+3) & 0x7FFFF;
R2=bset R2 by 19;
dm(TCB2)=R2;
R2=(TCB2+3) & 0x7FFFF;
R2=bclr R2 by 19;
dm(TCB1)=R2;
dm(CPx)=R2;

Inserting a TCB in an Active Chain


This is supported by serial ports only. The SPI interface does not
support inserting a TCB in an active chain.
It is possible to insert a single DMA operation or another DMA chain
within an active DMA chain. Programs may need to perform insertion
when a high priority DMA requires service and cannot wait for the cur-
rent chain to finish.
When DMA on a channel is disabled and chaining on the channel is
enabled, the DMA channel is in chain insertion mode. This mode lets a
program insert a new DMA or DMA chain within the current chain with-
out effecting the current DMA transfer. Use the following sequence to
insert a DMA subchain for the serial port 0A channel while another chain
is active:
7-16
/* clear CPx register */
/* init DMA control registers and
load IIx address of next TCB and
mask address */
/* set PCI bit */
/* write address to CPx location of
current TCB */
/* load IIx address of next TCB and
mask address*/
/* clear PCI bit */
/* write address to CPx location of
current TCB */
/* write IIx address of TCB1 to CPx
register to start chaining*/
ADSP-2126x SHARC Processor Hardware Reference