參數(shù)資料
型號(hào): CYD18S72V
廠商: Cypress Semiconductor Corp.
英文描述: FLEx72 3.3V 64K/128K/256K x 72 Synchronous Dual-Port RAM(FLEx72 3.3V 64K/128K/256K x 72同步雙端口RAM)
中文描述: FLEx72 3.3 64K/128K/256K × 72同步雙口RAM(FLEx72 3.3 64K/128K/256K × 72同步雙端口RAM)的
文件頁(yè)數(shù): 6/25頁(yè)
文件大?。?/td> 677K
代理商: CYD18S72V
Document #: 38-06069 Rev. *I
Page 6 of 25
CYD04S72V
CYD09S72V
CYD18S72V
Address Counter and Mask Register Operations
[17]
This section describes the features only apply to 4 Mbit and 9
Mbit devices, not to 18 Mbit device. Each port have a program-
mable burst address counter. The burst counter contains three
registers: a counter register, a mask register, and a mirror
register.
The
counter register
contains the address used to access the
RAM array. It is changed only by the Counter Load, Increment,
Counter Reset, and by master reset (MRST) operations.
The
mask register
value affects the Increment and Counter
Reset operations by preventing the corresponding bits of the
counter register from changing. It also affects the counter
interrupt output (CNTINT). The mask register is changed only
by the Mask Load and Mask Reset operations, and by the
MRST. The mask register defines the counting range of the
counter register. It divides the counter register into two
regions: zero or more “0s” in the most significant bits define
the masked region, one or more “1s” in the least significant bits
define the unmasked region. Bit 0 may also be “0,” masking
the least significant counter bit and causing the counter to
increment by two instead of one.
The mirror register
is used to reload the counter register on
increment operations (see “retransmit,” below). It always
contains the value last loaded into the counter register, and is
changed only by the Counter Load, and Counter Reset opera-
tions, and by the MRST.
Table 3
summarizes the operation of these registers and the
required input control signals. The MRST control signal is
Notes:
15.X” = “Don’t Care,” “H” = HIGH, “L” = LOW.
16.Counter operation and mask register operation is independent of chip enables.
17.The CYD04S72V has 16 address bits and a maximum address value of FFFF. The CYD09S72V has 17 address bits and a maximum address value of 1FFFF.
The CYD18S72V has 18 address bits and a maximum address value of 3FFFF.
asynchronous. All the other control signals in
Table 3
(CNT/MSK, CNTRST, ADS, CNTEN) are synchronized to the
port’s CLK. All these counter and mask operations are
independent of the port’s chip enable inputs (CE0 and CE1).
Counter enable (CNTEN) inputs are provided to stall the
operation of the address input and utilize the internal address
generated by the internal counter for fast, interleaved memory
applications. A port’s burst counter is loaded when the port’s
address strobe (ADS) and CNTEN signals are LOW. When the
port’s CNTEN is asserted and the ADS is deasserted, the
address counter will increment on each LOW to HIGH
transition of that port’s clock signal. This will Read/Write one
word from/into each successive address location until CNTEN
is deasserted. The counter can address the entire memory
array, and will loop back to the start. Counter reset (CNTRST)
is used to reset the unmasked portion of the burst counter to
0s. A counter-mask register is used to control the counter
wrap.
Counter Reset Operation
All unmasked bits of the counter and mirror registers are reset
to “0.” All masked bits remain unchanged. A Mask Reset
followed by a Counter Reset will reset the counter and mirror
registers to 00000, as will master reset (MRST).
Counter Load Operation
The address counter and mirror registers are both loaded with
the address value presented at the address lines.
Table 3. Address Counter and Counter Mask Register Control Operation (Any Port)
[15,16]
CLK
MRST CNT/MSK CNTRST
ADS
CNTEN
Operation
Description
X
L
X
X
X
X
Master Reset
Reset address counter to all 0s and mask register
to all 1s
H
H
L
X
X
Counter Reset
Reset counter unmasked portion to all 0s
H
H
H
L
L
Counter Load
Load counter with external address value presented
on address lines
H
H
H
L
H
Counter Readback Read out counter internal value on address lines
H
H
H
H
L
Counter Increment Internally increment address counter value
H
H
H
H
H
Counter Hold
Constantly hold the address value for multiple clock
cycles
H
L
L
X
X
Mask Reset
Reset mask register to all 1s
H
L
H
L
L
Mask Load
Load mask register with value presented on the
address lines
H
L
H
L
H
Mask Readback
Read out mask register value on address lines
H
L
H
H
X
Reserved
Operation undefined
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