adsp-2186n Analog Devices, Inc., adsp-2186n Datasheet - Page 13

• Manufacturer Part Number: adsp-2186n
• Description: Dsp Microcomputer
• Manufacturer: Analog Devices, Inc.

The BDMA circuit supports four different data formats that are
selected by the BTYPE register field. The appropriate number of
8-bit accesses are done from the byte memory space to build the
word size selected.
the BDMA circuit.
Table 7. Data Formats
Unused bits in the 8-bit data memory formats are filled with 0s.
The BIAD register field is used to specify the starting address for
the on-chip memory involved with the transfer. The 14-bit
BEAD register specifies the starting address for the external byte
memory space. The 8-bit BMPAGE register specifies the start-
ing page for the external byte memory space. The BDIR register
field selects the direction of the transfer. Finally, the 14-bit
BWCOUNT register specifies the number of DSP words to
transfer and initiates the BDMA circuit transfers.
BDMA accesses can cross page boundaries during sequential
addressing. A BDMA interrupt is generated on the completion
of the number of transfers specified by the BWCOUNT register.
The BWCOUNT register is updated after each transfer so it can
be used to check the status of the transfers. When it reaches
zero, the transfers have finished and a BDMA interrupt is gener-
ated. The BMPAGE and BEAD registers must not be accessed
by the DSP during BDMA operations.
The source or destination of a BDMA transfer will always be on-
chip program or data memory.
When the BWCOUNT register is written with a nonzero value
the BDMA circuit starts executing byte memory accesses with
wait states set by BMWAIT. These accesses continue until the
count reaches zero. When enough accesses have occurred to
create a destination word, it is transferred to or from on-chip
memory. The transfer takes one DSP cycle. DSP accesses to
external memory have priority over BDMA byte mem-
ory accesses.
BTYPE
00
01
10
11
15 14 13 12 11 10
0
0
0
BMPAGE
0
Internal Memory
Space
Program Memory
Data Memory
Data Memory
Data Memory
0
Figure 13. BDMA Control Register
0
Table 7
BDMA CONTROL
9
0
8
0
(SEE TABLE 12)
shows the data formats supported by
7
0
OVERLAY
BDMA
6
0
BITS
5
0
Word Size
24
16
8
8
4
0
3
1
2
0
BCR
0 = RUN DURING BDMA
1 = HALT DURING BDMA
1
BTYPE
0
BDIR
0 = LOAD FROM BM
1 = STORE TO BM
0
0
Alignment
Full Word
Full Word
MSBs
LSBs
Rev. A | Page 13 of 48 | August 2006
DM (0x3FE3)
The BDMA Context Reset bit (BCR) controls whether the pro-
cessor is held off while the BDMA accesses are occurring.
Setting the BCR bit to 0 allows the processor to continue opera-
tions. Setting the BCR bit to 1 causes the processor to stop
execution while the BDMA accesses are occurring, to clear the
context of the processor, and start execution at address 0 when
the BDMA accesses have completed.
The BDMA overlay bits specify the OVLAY memory blocks to
be accessed for internal memory. Set these bits as indicated in
Figure
Note: BDMA cannot access external overlay memory regions 1
and 2.
The BMWAIT field, which has four bits on ADSP-218xN series
members, allows selection up to 15 wait states for BDMA
transfers.
Internal Memory DMA Port (IDMA Port; Host Memory
Mode)
The IDMA Port provides an efficient means of communication
between a host system and ADSP-218xN series members. The
port is used to access the on-chip program memory and data
memory of the DSP with only one DSP cycle per word over-
head. The IDMA port cannot, however, be used to write to the
DSP’s memory-mapped control registers. A typical IDMA
transfer process is shown as follows:
Table 8. IDMA/BDMA Overlay Bits
Processor
ADSP-2184N
ADSP-2185N
ADSP-2186N
ADSP-2187N
ADSP-2188N
ADSP-2189N
1. Host starts IDMA transfer.
2. Host checks IACK control line to see if the DSP is busy.
3. Host uses IS and IAL control lines to latch either the DMA
4. Host uses IS and IRD (or IWR) to read (or write) DSP
5. Host checks IACK line to see if the DSP has completed the
6. Host ends IDMA transfer.
starting address (IDMAA) or the PM/DM OVLAY selec-
tion into the DSP’s IDMA control registers. If Bit 15 = 1,
the values of Bits 7–0 represent the IDMA overlay; Bits
14–8 must be set to 0. If Bit 15 = 0, the value of Bits 13–0
represent the starting address of internal memory to be
accessed and Bit 14 reflects PM or DM for access. Set
IDDMOVLAY and IDPMOVLAY bits in the IDMA over-
lay register as indicted in
internal memory (PM or DM).
previous IDMA operation.
13.
IDMA/BDMA
PMOVLAY
0
0
0
0, 4, 5
0, 4, 5, 6, 7
0, 4, 5
Table
8.
IDMA/BDMA
DMOVLAY
0
0
0
0, 4, 5
0, 4, 5, 6, 7, 8
0, 4, 5, 6, 7
ADSP-218xN