Programming Model

rom a en When rom a en is set, accesses to Block A ROM/Flash in the address range selected by ROM A BASE are enabled. When rom a en is cleared, they are disabled.

rom a we When rom a we is set, writes to Block A ROM/Flash are enabled. When rom a we is cleared, they are disabled. Note that if rom_a_64 is cleared, only one-byte writes are allowed. If rom_a_64 is set, only four-byte writes are allowed. The Falcon ignores other writes. If a valid write is attempted and rom a we is cleared, the write does not happen but the cycle is terminated normally. Refer to Table 3-16for details of ROM/Flash accesses.

Table 3-16. Read/Write to ROM/Flash

Cycle

Transfer

Alignment

rom_x_64

rom_x_we

Falcon Response

Size

 

 

 

 

 

 

 

 

 

 

 

Write

1-byte

X

0

0

Normal termination, but

 

 

 

 

 

no write to ROM/Flash

 

 

 

 

 

 

Write

1-byte

X

0

1

Normal termination,

 

 

 

 

 

write occurs to

 

 

 

 

 

ROM/Flash

 

 

 

 

 

 

Write

1-byte

X

1

X

No Response

 

 

 

 

 

 

Write

4-byte

Misaligned

X

X

No Response

 

 

 

 

 

 

Write

4-byte

Aligned

0

X

No Response

 

 

 

 

 

 

Write

4-byte

Aligned

1

0

Normal termination, but

 

 

 

 

 

no write to ROM/Flash

 

 

 

 

 

 

Write

4-byte

Aligned

1

1

Normal termination,

 

 

 

 

 

write occurs to

 

 

 

 

 

ROM/Flash

 

 

 

 

 

 

Write

2,3,5,6,7,

X

X

X

No Response

 

8,32-byte

 

 

 

 

 

 

 

 

 

 

Read

X

X

X

X

Normal Termination

 

 

 

 

 

 

3

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Image 209
Motorola MVME2300 Series manual Read/Write to ROM/Flash, Cycle Transfer Alignment Romx64 Romxwe Falcon Response