4 smc mode register – Rainbow Electronics AT91CAP9S250A User Manual
Page 209
209
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
22.14.4
SMC MODE Register
Register Name:
SMC_MODE[0..
5
]
Access Type:
Read/Write
• READ_MODE:
1: The read operation is controlled by the NRD signal.
– If TDF cycles are programmed, the external bus is marked busy after the rising edge of NRD.
– If TDF optimization is enabled (TDF_MODE =1), TDF wait states are inserted after the setup of NRD.
0: The read operation is controlled by the NCS signal.
– If TDF cycles are programmed, the external bus is marked busy after the rising edge of NCS.
– If TDF optimization is enabled (TDF_MODE =1), TDF wait states are inserted after the setup of NCS.
• WRITE_MODE
1: The write operation is controlled by the NWE signal.
– If TDF optimization is enabled (TDF_MODE =1), TDF wait states will be inserted after the setup of NWE.
0: The write operation is controlled by the NCS signal.
– If TDF optimization is enabled (TDF_MODE =1), TDF wait states will be inserted after the setup of NCS.
• EXNW_MODE: NWAIT Mode
The NWAIT signal is used to extend the current read or write signal. It is only taken into account during the pulse phase of
the read and write controlling signal. When the use of NWAIT is enabled, at least one cycle hold duration must be pro-
grammed for the read and write controlling signal.
• Disabled Mode: The NWAIT input signal is ignored on the corresponding Chip Select.
• Frozen Mode: If asserted, the NWAIT signal freezes the current read or write cycle. After deassertion, the read/write
cycle is resumed from the point where it was stopped.
• Ready Mode: The NWAIT signal indicates the availability of the external device at the end of the pulse of the controlling
read or write signal, to complete the access. If high, the access normally completes. If low, the access is extended until
NWAIT returns high.
31
30
29
28
27
26
25
24
–
–
PS
–
–
–
PMEN
23
22
21
20
19
18
17
16
–
–
–
TDF_MODE
TDF_CYCLES
15
14
13
12
11
10
9
8
–
–
DBW
–
–
–
BAT
7
6
5
4
3
2
1
0
–
–
EXNW_MODE
–
–
WRITE_MODE
READ_MODE
EXNW_MODE
NWAIT Mode
0
0
Disabled
0
1
Reserved
1
0
Frozen Mode
1
1
Ready Mode