MT42L256M32D4KP-3 IT:A【PDF 84/164 页】IC LPDDR2 SDRAM 8GBIT 168FBGA

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2Gb: x16, x32 Mobile LPDDR2 SDRAM S4

SELF REFRESH Operation

The mask bit to the bank enables or disables a refresh operation of the entire memory

space within the bank. If a bank is masked using the bank mask register, a REFRESH op-

eration to the entire bank is blocked and bank data retention is not guaranteed in self

refresh mode. To enable a REFRESH operation to a bank, the corresponding bank mask

bit must be programmed as “unmasked.” When a bank mask bit is unmasked, the array

space being refreshed within that bank is determined by the programmed status of the

segment mask bits.

Partial-Array Self Refresh – Segment Masking

Programming segment mask bits is similar to programming bank mask bits. For densi-

ties 1Gb and higher, eight segments are used for masking (see the MR17 PASR Segment

Mask (MA[7:0] = 011h) and MR17 PASR Segment Mask Definitions tables). A mode reg-

ister is used for programming segment mask bits up to eight bits. For densities less than

1Gb, segment masking is not supported.

When the mask bit to an address range (represented as a segment) is programmed as

“masked,” a REFRESH operation to that segment is blocked. Conversely, when a seg-

ment mask bit to an address range is unmasked, refresh to that segment is enabled.

A segment masking scheme can be used in place of or in combination with a bank

masking scheme. Each segment mask bit setting is applied across all banks. For seg-

ment masking bit assignments, see the tables noted above.

Table 45: Bank and Segment Masking Example

Segment Mask (MR17) Bank 0 Bank 1 Bank 2 Bank 3 Bank 4 Bank 5 Bank 6 Bank 7

Bank Mask (MR16)

0

1

0

0

0

0

0

1

Segment 0

Segment 1

Segment 2

Segment 3

Segment 4

Segment 5

Segment 6

Segment 7

0

0

1

0

0

0

0

1

–

–

M

–

–

–

–

M

M

M

M

M

M

M

M

M

–

–

M

–

–

–

–

M

–

–

M

–

–

–

–

M

–

–

M

–

–

–

–

M

–

–

M

–

–

–

–

M

–

–

M

–

–

–

–

M

M

M

M

M

M

M

M

M

Note:

1. This table provides values for an 8-bank device with REFRESH operations masked to

banks 1 and 7, and segments 2 and 7.

PDF: 09005aef83f3f2eb

2gb_mobile_lpddr2_s4_g69a.pdf – Rev. N 3/12 EN

84

Micron Technology, Inc. reserves the right to change products or specifications without notice.

2010 Micron Technology, Inc. All rights reserved.

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MT42L256M32D4KP-MS 制造商:Micron Technology Inc 功能描述:256MX32 LPDDR2 PLASTIC IND TEMP GREEN WFBGA 1.2V - Bulk