10 / 15 page
CY7C470
CY7C472
CY7C474
10
Table 1. Flag Truth Table[13]
HF
E/F
PAFE
State
CY77C470
(8K x 9)
Number of Words
in FIFO
CY77C472
(16K x 9)
Number of Words in
FIFO
CY77C474
(32K x 9)
Number of Words in
FIFO
1
0
0
Empty
0
0
0
1
1
0
Almost Empty
1
⇒(P – 1)
1
⇒ (P – 1)
1
⇒ (P – 1)
1
1
1
Less than Half Full
P
⇒ 4096
P
⇒ 8192
P
⇒ 16384
0
1
1
Greater than Half Full
4097
⇒ (8192 – P)
8193
⇒ (16384 – P)
16385
⇒ (32768 – P)
0
1
0
Almost Full
(8192 – P+1)
⇒ 8191
(16384 – P+1)
⇒ 16383
(32768 – P+1)
⇒ 32767
0
0
0
Full
8192
16384
32768
Table 2. Programmable Almost Full/Empty Options[14]
D3
D2
D1
D0
PAFE Active when:
P
0
0
0
0
256 or less locations from Empty/Full (default)
256
0
0
0
1
16 or less locations from Empty/Full
16
0
0
1
0
32 or less locations from Empty/Full
32
0
0
1
1
64 or less locations from Empty/Full
64
0
1
0
0
128 or less locations from Empty/Full
128
0
1
0
1
256 or less locations from Empty/Full (default)
256
0
1
1
0
512 or less locations from Empty/Full
512
0
1
1
1
1024 or less locations from Empty/Full
1024
1
0
0
0
2048 or less locations from Empty/Full
2048
1
0
0
1
4098 or less locations from Empty/Full[15]
4098
1
0
1
0
8192 or less locations from Empty/Full[16]
8192
Notes:
13. See
Table 2 for P values.
14. Almost flags default to 256 locations from Empty/Full.
15. Only for CY7C472 and CY7C474.
16. Only for CY7C470.