10
Memory Interface
10 – 35
labels to I/O memory addresses, use a
#define
macro. The best use of
the .PORT directive is in porting non-ADSP-2181 applications to the
ADSP-2181; otherwise, use I/O memory space for memory-mapped I/O.
10.6.5
ADSP-2181 Composite Memory Select
The ADSP-2181 has a programmable memory select signal, Composite
Memory Select (
CMS
). This signal lets you generate a memory select for
devices mapped to more than one memory space, with the same timing as
other individual memory select signals (
PMS
,
DMS
,
BMS
, and
IOMS
).
Based on the value of CMSSEL in the Programmable Flag & Composite
Select Control register (see Figure 10.33), the ADSP-2181 asserts
CMS
Figure 10.33 CMSSEL Selection for
CMS
CMS
CMS
CMS
CMS
Signal
when the corresponding memory select signal (or signals) are asserted. Each
xMS
signal can be individually enabled. After reset, CMSSEL is initialized to
enable
PMS
,
DMS
, and
IOMS
(with
BMS
disabled).
Figure 10.26 (earlier in this chapter) shows an example of how to use the
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
BMWAIT
1
0
1
1
1
1
0
Programmable Flag & Composite Select Control
PFTYPE
1 = Output
0 = Input
1
0
0
0
0
CMSSEL
1 = Enable CMS
0 = Disable CMS
DM(0x3FE6)
0
0
0
0
DM
BM
IOM
PM