7C4271V-15 Просмотр технического описания (PDF) - Cypress Semiconductor
Номер в каталоге
Компоненты Описание
производитель
7C4271V-15 Datasheet PDF : 16 Pages
| |||
CY7C4261V/CY7C4271V
CY7C4281V/CY7C4291V
16k x 9
87
0
Empty Offset (LSB) Reg.
Default Value = 007h
8
5
0
(MSB)
Default Value = 000h
87
0
Full Offset (LSB) Reg
Default Value = 007h
8
5
0
(MSB)
Default Value = 000h
64k x 9
87
0
Empty Offset (LSB) Reg.
Default Value = 007h
32k x 9
87
0
Empty Offset (LSB) Reg.
Default Value = 007h
86
0
(MSB)
Default Value = 000h
87
0
Full Offset (LSB) Reg
Default Value = 007h
86
0
(MSB)
Default Value = 000h
128k x 9
87
0
Empty Offset (LSB) Reg.
Default Value = 007h
contents to the data outputs. Writes and reads should not be
performed simultaneously on the offset registers.
Programmable Flag (PAE, PAF) Operation
Whether the flag offset registers are programmed as
described in Table 1 or the default values are used, the
programmable almost-empty flag (PAE) and programmable
almost-full flag (PAF) states are determined by their corre-
sponding offset registers and the difference between the read
and write pointers.
Table 1. Writing the Offset Registers[1]
LD WEN WCLK
Selection
0
0
Empty Offset (LSB)
Empty Offset (MSB)
Full Offset (LSB)
Full Offset (MSB)
0
1
No Operation
1
0
Write Into FIFO
87
0
(MSB)
Default Value = 000h
8
0
(MSB)
Default Value = 000h
1
1
No Operation
87
0
Full Offset (LSB) Reg
Default Value = 007h
87
0
(MSB)
Default Value = 000h
87
0
Full Offset (LSB) Reg
Default Value = 007h
8
0
(MSB)
Default Value = 000h
The number formed by the empty offset least significant bit
register and empty offset most significant bit register is
referred to as n and determines the operation of PAE. PAF is
synchronized to the LOW-to-HIGH transition of RCLK by one
flip-flop and is LOW when the FIFO contains n or fewer unread
words. PAE is set HIGH by the LOW-to-HIGH transition of
RCLK when the FIFO contains (n+1) or greater unread words.
Figure 1. Offset Register Location and Default Values
It is not necessary to write to all the offset registers at one time.
A subset of the offset registers can be written; then by bringing
the WEN2/LD input HIGH, the FIFO is returned to normal read
and write operation. The next time WEN2/LD is brought LOW,
a write operation stores data in the next offset register in
sequence.
The contents of the offset registers can be read to the data
outputs when WEN2/LD is LOW and both REN1 and REN2
are LOW. LOW-to-HIGH transitions of RCLK read register
The number formed by the full offset least significant bit
register and full offset most significant bit register is referred to
as m and determines the operation of PAF. PAE is synchronized
to the LOW-to-HIGH transition of WCLK by one flip-flop and is
set LOW when the number of unread words in the FIFO is
greater than or equal to CY7C4261V (16k – m), CY7C4271V
(32k – m), CY7C4281V (64k – m) and CY7C4291V
(128k – m). PAF is set HIGH by the LOW-to-HIGH transition
of WCLK when the number of available memory locations is
greater than m.
Note:
1. The same selection sequence applies to reading from the registers. REN1 and REN2 are enabled and a read is performed on the LOW-to-HIGH transition of RCLK.
Document #: 38-06013 Rev. *B
Page 4 of 16
Share Link: 