MAC7200 datasheet(304/976 Pages) FREESCALE

304 / 976 page

The SPP DMA Controller Module (SPP_DMA2)

MAC7200 Microcontroller Family Reference Manual, Rev. 2

226

Freescale Semiconductor

Figure 12-19 and Table 12-23 define word 2 of the TCDn structure, the nbytes field.

Figure 12-20 and Table 12-24 define word 3 of the TCDn structure, the slast field.

nbytes[31:16]

Reset

————————————————

9876543210

nbytes[15:00]

Reset

————————————————

= Unimplemented

Figure 12-19. TCDn Word 2 (TCDn.nbytes) Field

Table 12-23. TCDn Word 2 (TCDn.nbytes) Field Description

Field

Description

31–0

nbytes[31:0]

Inner “minor” byte transfer count. Number of bytes to be transferred in each service request of the channel. As a

channel is activated, the contents of the appropriate TCD is loaded into the dma_engine, and the appropriate

reads and writes performed until the complete byte transfer count has been transferred. This is an indivisible

operation and cannot be stalled or halted. Once the minor count is exhausted, the current values of the saddr and

daddr are written back into the local memory, the major iteration count is decremented and restored to the local

memory. If the major iteration count is completed, additional processing is performed. The nbytes value

0x0000_0000 is interpreted as 0x1_0000_0000, thus specifying a 4GB transfer.

MAC7200 Datasheet(PDF) 304 Page - Freescale Semiconductor, Inc