Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK データシート

 185

SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

Byte write access supports one byte write signal per byte of the data bus and a single read signal.

Note that the SMC does not allow boot in Byte Write Access mode. 

• For 16-bit devices: the SMC provides NWR0 and NWR1 write signals for respectively byte0 (lower byte) and 

byte1 (upper byte) of a 16-bit bus. One single read signal (NRD) is provided. 

Byte Write Access is used to connect 2 x 8-bit devices as a 16-bit memory. 

• For 32-bit devices: NWR0, NWR1, NWR2 and NWR3, are the write signals of byte0 (lower byte), byte1, byte2 

and byte 3 (upper byte) respectively. One single read signal (NRD) is provided.

Byte Write Access is used to connect 4 x 8-bit devices as a 32-bit memory.

In this mode, read/write operations can be enabled/disabled at a byte level. One byte-select line per byte of the
data bus is provided. One NRD and one NWE signal control read and write.

• For 16-bit devices: the SMC provides NBS0 and NBS1 selection signals for respectively byte0 (lower byte) and 

byte1 (upper byte) of a 16-bit bus. 

Byte Select Access is used to connect one 16-bit device.

• For 32-bit devices: NBS0, NBS1, NBS2 and NBS3, are the selection signals of byte0 (lower byte), byte1, byte2 

and byte 3 (upper byte) respectively. Byte Select Access is used to connect two 16-bit devices.

 shows how to connect two 16-bit devices on a 32-bit data bus in Byte Select Access mode, on NCS3

(BAT = Byte Select Access).

 Connection of 2 x 8-bit Devices on a 16-bit Bus: Byte Write Option

SMC

A1

NWR0

NRD

NCS[3]

Write Enable

Read Enable

Memory Enable

NWR1

Write Enable

Read Enable

Memory Enable

D[7:0]

D[7:0]

D[15:8]

D[15:8]

A[24:2]

A[23:1]

A[23:1]

A[0]

A[0]