Rainbow Electronics AT91CAP9S250A - Manual (Page 269)

269
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
Figure 25-2. Parity Generation for 512/1024/2048/4096 8-bit Words1
To calculate P8’ to PX’ and P8 to PX, apply the algorithm that follows.
Page size = 2 n
for i =0 to n
begin
for (j = 0 to page_size_byte)
begin
if(j[i] ==1)
P[2 i+3 ]=bit7(+)bit6(+)bit5(+)bit4(+)bit3(+)
bit2(+)bit1(+)bit0(+)P[2 i+3 ]
else
P[2 i+3 ]’=bit7(+)bit6(+)bit5(+)bit4(+)bit3(+)
bit2(+)bit1(+)bit0(+)P[2 i+3 ]'
end
end
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
P8
P8'
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
P8
P8'
P16
P16'
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
P8
P8'
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
P8
P8'
P16
P16'
P32
P32
1st byte
P32
2nd byte
3rd byte
4 th byte
Page size th byte
(page size -1 )th byte
PX
PX'
Page size = 512 Px = 2048
Page size = 1024 Px = 4096
Page size = 2048 Px = 8192
Page size = 4096 Px = 16384
(page size -2 )th byte
(page size -3 )th byte
P1 P1' P1' P1 P1 P1' P1' P1
P2 P2' P2 P2'
P4 P4'
P1=bit7(+)bit5(+)bit3(+)bit1(+)P1
P2=bit7(+)bit6(+)bit3(+)bit2(+)P2
P4=bit7(+)bit6(+)bit5(+)bit4(+)P4
P1'=bit6(+)bit4(+)bit2(+)bit0(+)P1'
P2'=bit5(+)bit4(+)bit1(+)bit0(+)P2'
P4'=bit7(+)bit6(+)bit5(+)bit4(+)P4'