Semiconductor memories. Memories 2/38 Types of semiconductor memories Memory chip parameters Chosen...

Semiconductor memories

Memories 2/38

Types of semiconductor memories

Memory chip parameters

Chosen types of memories

Memory map

Timings

Memories 3/38

timersRTC

address decoders

memory servicing devices

interruptcontrollers

secondarymemories.

processor

programme memory(ROM)

datamemory(RAM)

operatordevices

commu-nication devices

process devicesmain memory

video memory

The application of semiconductor memories:

semiconductor disksconfigur. memory

buffering memories

Memories - types 4/38


shiftingregisters

CCD - charge coupling

devices

with sequence access

volatile non-volatile

static dynamic (SRAM) (DRAM)

parallel classic (bipol.,unipol.) (unipol.)

serial pseudo-static (unipol.) (unipol.)

standard

memory losingdata duringpower off

memory keepingdata duringpower off

Memories - SRAM 5/38

Single bit of SRAM:

RDamplifier

wordselectline

+U

+U

bipolar

wordselectline

RDamplifier

Udd

Udd

Uss=0

unipolar


read

ADR

CE

R/W

D0..D7

Typical read and write cycles of SRAM

write

ADR

CE

R/W

D0..D7


SRAM examples:

symbol manufacturer organization access time[ns]

ICC/ISB 1

[mA]2114A Intel 1kx4 100-250 70/-

HM6116-12 Hitachi 2kx8 120 80/15

HM6264P Hitachi 8kx8 100-150 110/3

HM62256P Hitachi 32kx8 85-150 70/3

FCB61C1025 Philips 128kx8 35-55 80/3

Memories - DRAM 8/38

DRAM single bit:

Uss=0

wordselectline

RDamplifier

resistor meansthe charge leakage

of real capacitor


Advantages Faults

low power consumption;

high speeds;

large capacities;

small cases.

data refresh needed

(the charge in DRAM cell should be refreshed

each 2-16ms);

multiplexed address lines;

non-standard control.


Basic cycles:

A8..A15A0..A7writing ADR

RAS

CAS

WE

DATA Din

A8..A15A0..A7reading ADR

RAS

CAS

DATA

tACAS

tARAS

Dout

WE = 1


modification A8..A15A0..A7ADR

RAS

CAS

WE

Dout

Din Din

Dout

page read

Dout

A8..A15A8..A15A0..A7ADR

RAS

CAS

DATA Dout

WE = 1


basic refresh cycle

row addressADR

RASWE = 1

CAS = 1

ADR

RAS

CAS

DATA

hidden refresh cycle

A8..A15REFA8..A15A0..A7

Dout

WE = 1


DRAM refresh techniques:

1. Burst refresh - for instance each 2ms processor is stopped

and the whole set of rows addresses needed for memory refresh is generated.

2. Cycle steal - generation of successive refresh addresses realised

in the moments, in which processor doesn’t used the system bus

(for example after op-code fetch), but there are situations that processor

is halted or held by DMA and refresh should be realised in other way.

Attention:

Modern DRAM chip have built-in refresh circuit.


Block structure of Siemens’

4Mx1b memory chip with

built-in refresh circuit:


A7..A13

A0..A6MPX DRAM

A0

A6

CAS RAS

ADR0...

ADR6

MREQ

RFSH

50ns

50nsthere are also special

DRAM control chips: 3242, 8202 (IBM PC)

Example of simple DRAM control circuit:


symbol organization cycle time[ns]

ICC/ISB

[mA]

HM4864-12 64kx1 120 55/3,5

HM50464-12 64kx4 120 60/3,5

HM50256-12 256kx1 120 83/4,5

TC511000-10 1Mx1 100 60/2

TC514256-85 256kx8 85 65/2

Examples of the classical DRAMs:


FPM DRAM (Fast Page Mode DRAM) - dedicated for x486 systems,

bus frequency up to 66MHz, typical wait timings 5-3-3-3.

EDO DRAM (Extended Data Out DRAM) - increased speed by possibility

transfer of the next address during previous read cycle, bus frequency up to

50MHz, typical wait timings 5-2-2-2.

BEDO DRAM (Burst EDO DRAM) - fast, bus frequency up to 100MHz, needs

special chipset, rarely used, typical wait timings 5-1-1-1.

SDRAM (Synchronous DRAM) - access time about 10ns, bus frequency 100MHz

and more (6ns at 143MHz), typical wait timings 5-1-1-1, possible simultaneous

access to both open pages, built-in auto-refresh.


DDR SDRAM (Double Data Rate SDRAM) - transfer on both slopes of the

clocking signal - double read speed of data blocks.

ESDRAM (Enhanced SDRAM) - internal SRAM buffers double memory

efficiency.

DRDRAM (Direct Rambus DRAM) - special fast buses with DRDRAM and

frequency up to 400MHz and transfer on both slopes of the clocking signal,

transfer 1,6-2,4GB/s, non-standard mechanical construction.

SLDRAM (Synchronous Link DRAM) - SDRAM extension, transfer speed up to

3,2GB/s, electrically and mechanically compatible with SDRAM.

SGRAM (Synchronous Graphic RAM) - fast (100MHz), single-port memory for

graphic applications.

VRAM (Video RAM) - fast, dual-port memory for graphic applications.

Memories - technologies 19/38

Technology features of memories:

Bipolar:

faster;

bigger power consumption;

lower integration scale;

„more expensive” 1 bit.

Unipolar:

slower;

smaller power consumption;

higher integration scale;

„more cheap” 1 bit.



shiftingregisters


devices






standardROM

PROM

EPROM (serial & parallel.)

EEPROM (E2PROM) (serial & parallel)

NVRAM (SRAM+EEPROM)

FLASH(3 types)

FRAM

bi- po-lar

uni-po-lar

u

n

i

p

o

l

a

r



Memories - ROM 21/38

Features:

• programmed only during manufacturing;

• long-lasting and expensive manufacturing cycle;

• programme error causes useless of whole chip series;

• expensive debugging (multiple re-designing of chip contents);

• low cost of single memory chip with debugged programme in mass manufacturing.

Memories - PROM 22/38

Single bit PROM:

word select line

Vcc

7V

Q0

Vcc

bit programming:Vcc=12,5V Up=8V

12,5V

12,5V

„0” - 0V

„1” - 8V

Ube

Memories - EPROM 23/38

Single bit EPROM:

DATA BUFFER

RD/WR AMPLIFIER

COLUMN DECODER

ROW

DECODER

ADDRESS

BUFFER

WE/CS

PROG

Memories - EPROM 24/38

EPROM examples:

symbol technology organization access time[ns]

ICC/ISB 1

[mA]

2764A-1 HMOS 8kx8 180 75/35

27C64-15 CHMOS 8kx8 150 20/0,1

27256-1 HMOS 32kx8 170 125/50

27C256-1 CHMOS 32kx8 170 30/0,1

27010-200 HMOS 128kx8 200 150/50

27210-150 HMOS 64kx16 150 170/50

Memories – EEPROM (E2PROM) 25/38

EEPROM (Electrically Erasable Programmable Read Only Memory) features :

• internal structure based on EPROM;

• additional transistor per each bit allows individual erasing and programming;

• higher number of reprogramming cycles;

• erasing and reprogramming can last up to 10ms;

• with parallel access – equivalent to EPROMs, or serial access (with I2C, SPI)- as a configuration memory;

• parallel EEPROMs can allow programming of blocks of bytes (64B, 128B, 256B): new data is buffered in local SRAM and then simultaneous programming of whole block starts.

Memories - NVRAM 26/38

Example of NVRAM structure:

Memories - NVRAM 27/38

the working of NVRAM:

operating of the built-in capacitor

Memories - FLASH 28/38

structure of storing transistor:


Types of the FLASH memories:

1. Standard - equivalent to EEPROM; with access time 70..200ns;

Ucc = 5V; Icc 30mA; examples: 28F256A, 28F512, 28F010, 28F020.

2. Flash file - internally divided into independent blocks of equal capacity (64kB);

access time: 70..200ns; Ucc = 5V or 3,3V; capacities.: 1MB, 4MB,

2Mx16; examples: 28F008SA, 28F016SA, DD28F032SA)


Types of the FLASH memories (cont.):

3. Boot-block flash - characteristic pin RP - Reset-Powerdown,

switching-off memory chip (ISB 0,05A); whole memory divided into

4 specific blocks:

• 8kB Boot Block for initial programme, down-loader;

• 2 x 4kB independent Parameter Block working as configuration memory

instead additional NVRAM or EEPROM chips;

• 112kB Main Block - for the rest of software.

access time 60-150ns; organization 8- or 16-bit; Ucc = 5V or 3,5V;


Two types of boot-block FLASH:

Blocks sequence depends

on target processor:

8kB Boot Block

4kB Param. Block4kB Param. Block

112kB Main Block

1FFFF

00000

dedicated for 8xx86 family

112kB Main Block

4kB Param. Block4kB Param. Block

8kB Boot Block

1FFFF

00000

dedicated for: MCS51, MCS96, MC68xx,

Z80, Z8000

Memories - FRAM 32/38

Single bit FRAM:

wordselectline

RDamplifier

+U

Uss=0

primary construction

wordselectline

RDamplifier

+U

Uss=0

modified construction

capacitor withferro-electric

Memories - FRAM 33/38

Available FRAMs:

• with serial interfaces: I2C (0,4..1MHz), SPI (2,1..5MHz);

• with parallel interface (for building main-memory blocks);



shiftingregisters


devices






standardROM

PROM

EPROM (serial & parallel.)

EEPROM (E2PROM) (serial & parallel)

NVRAM (SRAM+EEPROM)

FLASH(3 types)

FRAM

bi- po-lar

uni-po-lar

u

n

i

p

o

l

a

r



zero-power RAM

MRAM, OUM, RRAM, polymer, nano-mechanical

Memories - zero-power RAM 35/38

Memory structure:

Memories - zero-power RAM 36/38

MRAM - magnetoresistive RAM, two magnetic layers separated by dielectric

OUM (Ovonic Unified Memory) - materials as in CD-RW disks, but writing and

reading realized electrically

RRAM - resistive memory, uses the material which alters its resistance under

electric field

polymer - utilization of the ion structure changes inside polymer under electric

field, high density of bit (also in 3D), transistors need only to control the memory

array

nano-mechanical - np. millipede IBMa

Memories - specific parameters 37/38

Specific parameters of semiconductor memory:

organization (1-bit, k-bit, byte);

capacity (number of data bits stored in chip);

supply parameters (operating voltage / data retention voltage,

operating current / standby current / data retention current);

volatile or non-volatile;

data outputs load capacity;

time characteristic (access time, cycle time, transfer speed).

Memories - specific parameters 38/38

Comparison of chosen memory types

type size data writing reading powerof 1 bit non-volatile time

[ns]number time

[ns]number consumption

SRAM large - 25-100 unlimit. 25-100 unlimit. low

DRAM middle - 50-100 unlimit. 30-70 unlimit. high

EEPROM middle + 10ms 105 60-150 unlimit. middle

NVRAM large + 25-45 unlimit. 25-45 unlimit. middle

Flash small + 5-10s 106 70-150 unlimit. middle

FRAM middle + 150-200 1010-1012 150-200 1010-1012 low

Semiconductor memories. Memories 2/38 Types of semiconductor memories Memory chip parameters Chosen...

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