Sdram_16bit register – Rainbow Electronics AT75C220 User Manual
Page 29
AT75C220
29
•
NR
Sets the number of row bits. Default is 11 row bits.
•
NB
Sets the number of banks. Default is two banks.
•
CAS
Sets the CAS latency. The SDMC has been modified so that it only supports a CAS latency of two. Writing to this reg-
ister will have no effect.
•
TWR
Sets the value of TWR expressed in number of cycles. Default is two cycles.
•
TRC
Sets the value of TRC expressed in number of cycles. Default is eight cycles.
•
TRP
Sets the value of TRP expressed in number of cycles. Default is three cycles.
•
TRCD
Sets the value of TRCD expressed in number of cycles. Default is three cycles.
•
TRAS
Sets the value of TRAS expressed in number of cycles. Default is five cycles.
SDRAM_16bit Register
Register Name: SDRAM_16BIT
Access Type: Read/write
Reset Value: 0x1
•
16BIT
This bit is used to set the width of the external memory. If this field is set, the address is assumed to be 16 bits wide. If
not set, the memory bus is assumed to be 32 bits wide.
NR
Row Bits
00
11
01
12
10
13
11
Reserved
NB
Number of Banks
0
2
1
4
31
30
29
28
27
26
25
24
–
–
–
–
–
–
–
–
23
22
21
20
19
18
17
16
–
–
–
–
–
–
–
–
15
14
13
12
11
10
9
8
–
–
–
–
–
–
–
–
7
6
5
4
3
2
1
0
–
–
–
–
–
–
–
16BIT