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| 型号： | AD73422 |
| 厂商： | Analog Devices, Inc. |
| 英文描述： | Dual Low Power CMOS Analog Front End with DSP Microcomputer(带DSP微计算机的双模拟前端) |
| 中文描述： | 双低功耗CMOS模拟前端（带DSP的微计算机的双模拟前端与DSP的微机） |
| 文件页数： | 28/36页 |
| 文件大小： | 396K |
| 代理商： | AD73422 |
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REV. 0
AD73422
–
28
–
Table XXIV. Wait States
Address Range
Wait State Register
0x000–0x1FF
0x200–0x3FF
0x400–0x5FF
0x600–0x7FF
IOWAIT0
IOWAIT1
IOWAIT2
IOWAIT3
Composite Memory Select (
CMS
)
The AD73422 has a programmable memory select signal that is
useful for generating memory select signals for memories mapped
to more than one space. The
CMS
signal is generated to have
the same timing as each of the individual memory select signals
(
PMS
,
DMS
,
BMS
,
IOMS
) but can combine their functionality.
Each bit in the CMSSEL register, when set, causes the
CMS
signal to be asserted when the selected memory select is as-
serted. For example, to use a 32K word memory to act as both
program and data memory, set the
PMS
and
DMS
bits in the
CMSSEL register and use the
CMS
pin to drive the chip select
of the memory; use either
DMS
or
PMS
as the additional
address bit.
The
CMS
pin functions like the other memory select signals,
with the same timing and bus request logic. A 1 in the enable bit
causes the assertion of the
CMS
signal at the same time as the
selected memory select signal. All enable bits default to 1 at
reset, except the
BMS
bit.
Boot Memory Select (
BMS
) Disable
The AD73422 also lets you boot the processor from one exter-
nal memory space while using a different external memory space
for BDMA transfers during normal operation. You can use the
CMS
to select the first external memory space for BDMA trans-
fers and
BMS
to select the second external memory space for
booting. The
BMS
signal can be disabled by setting Bit 3 of the
System Control Register to 1. The System Control Register is
illustrated in Figure 17.
SYSTEM CONTROL REGISTER
9
8
PWAIT
PROGRAM MEMORY
WAIT STATES
0
0
0
0
0
1
0
0
0
0
0
0
0
1
1
1
15 14 13 12 11 10
7
6
5
4
3
2
1
0
DM (0 3FFF)
BMS
ENABLE
0 = ENABLED
1 = DISABLED
SPORT0 ENABLE
1 = ENABLED
0 = DISABLED
SPORT1 ENABLE
1 = ENABLED
0 = DISABLED
SPORT1 CONFIGURE
1 = SERIAL PORT
0 = FI, FO,
IRQ0
,
IRQ1
, SCLK
Figure 17. System Control Register
Byte Memory
The byte memory space is a bidirectional, 8-bit-wide, external
memory space used to store programs and data. Byte memory is
accessed using the BDMA feature. The BDMA Control Regis-
ter is shown in Figure 18. The byte memory space consists of
256 pages, each of which is 16K
×
8.
The byte memory space on the AD73422 supports read and
write operations as well as four different data formats. The byte
memory uses data bits 15:8 for data. The byte memory uses
data bits 23:16 and address bits 13:0 to create a 22-bit address.
This allows up to a 4 meg
×
8 (32 megabit) ROM or RAM to be
used without glue logic. All byte memory accesses are timed by
the BMWAIT register.
Byte Memory DMA (BDMA, Full Memory Mode)
The Byte memory DMA controller allows loading and storing of
program instructions and data using the byte memory space.
The BDMA circuit is able to access the byte memory space
while the processor is operating normally, and steals only one
DSP cycle per 8-, 16- or 24-bit word transferred.
BDMA CONTROL
9
8
BMPAGE
BTYPE
BCR
0 = RUN DURING BDMA
1 = HALT DURING BDMA
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
15 14 13 12 11 10
7
6
5
4
3
2
1
0
DM (0 3FE3)
BDIR
0 = LOAD FROM BM
1 = STORE TO BM
Figure 18. BDMA Control Register
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. Table XXV shows the data formats sup-
ported by the BDMA circuit.
Table XXV. Data Formats
Internal
Memory Space
BTYPE
Word Size
Alignment
00
01
10
11
Program Memory
Data Memory
Data Memory
Data Memory
24
16
8
8
Full Word
Full Word
MSBs
LSBs
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
starting 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 exter-
nal memory have priority over BDMA byte memory accesses.
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