User Manual

AT75C220

• 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

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

31 30 29 28 27 26 25 24

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23 22 21 20 19 18 17 16

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15 14 13 12 11 10 9 8

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76543210

–––––––16BIT