![Altera Cyclone IV Скачать руководство пользователя страница 39](http://html1.mh-extra.com/html/altera/cyclone-iv/cyclone-iv_device-handbook_2910785039.webp)
Chapter 3: Memory Blocks in Cyclone IV Devices
3–3
Overview
November 2011
Altera Corporation
Control Signals
The clock-enable control signal controls the clock entering the input and output
registers and the entire M9K memory block. This signal disables the clock so that the
M9K memory block does not see any clock edges and does not perform any
operations.
The
rden
and
wren
control signals control the read and write operations for each port
of M9K memory blocks. You can disable the
rden
or
wren
signals independently to
save power whenever the operation is not required.
Parity Bit Support
Parity checking for error detection is possible with the parity bit along with internal
logic resources. Cyclone IV devices M9K memory blocks support a parity bit for each
storage byte. You can use this bit as either a parity bit or as an additional data bit. No
parity function is actually performed on this bit.
Byte Enable Support
Cyclone IV devices M9K memory blocks support byte enables that mask the input
data so that only specific bytes of data are written. The unwritten bytes retain the
previous written value. The
wren
signals, along with the byte-enable (
byteena
)
signals, control the write operations of the RAM block. The default value of the
byteena
signals is high (enabled), in which case writing is controlled only by the
wren
signals. There is no clear port to the
byteena
registers. M9K blocks support byte
enables when the write port has a data width of ×16, ×18, ×32, or ×36 bits.
Byte enables operate in one-hot manner, with the LSB of the
byteena
signal
corresponding to the least significant byte of the data bus. For example, if
byteena = 01
and you are using a RAM block in ×18 mode,
data[8..0]
is enabled
and
data[17..9]
is disabled. Similarly, if
byteena = 11
, both
data[8..0]
and
data[17..9]
are enabled. Byte enables are active high.
lists the byte selection.
Table 3–2. byteena for Cyclone IV Devices M9K Blocks
byteena[3..0]
Affected Bytes
datain
×
16
datain
×
18
datain
×
32
datain
×
36
[0] = 1
[7..0]
[8..0]
[7..0]
[8..0]
[1] = 1
[15..8]
[17..9]
[15..8]
[17..9]
[2] = 1
—
—
[23..16]
[26..18]
[3] = 1
—
—
[31..24]
[35..27]
(1) Any combination of byte enables is possible.
Содержание Cyclone IV
Страница 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 106: ...II 2 Section II I O Interfaces Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 164: ...III 2 Section III System Integration Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Страница 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 276: ...viii Chapter Revision Dates Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 280: ...I 2 Section I Transceivers Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Страница 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Страница 442: ...vi Chapter Revision Dates Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Страница 446: ......