VME Bus

Versa Module Europa
IEEE 1014-1987

[VME Description]
[VME Standards] [VME Pin-Out] [VME Connectors]
[VME Card Dimensions [Form Factor]] [VME Data Transfer Timing] [VME ICs]
[VME Circuit Block Diagram] [VME COTs Cards] [VME Chassis Info]
[VME P2 BUS(s) Add-On Design] [VXI Design Info]

VME Bus Description

VME Bus Modules Interconnection
VMEbus System configuration

VME Bus Description
The VME bus is a scalable backplane bus interface.
VME Cards may be produced which respond to the following
Address widths or Data widths:
A01 - A15, A01 - A23, A01 - A31, or A01 - A40
D00 - D07, D00 - D15, D00 - D23, D00 - D31, or D00 - D63 (undefined before Rev. C).
The tables below detail the required control signals to produce the different bus widths.
Three main types of cards reside on the VME bus. The Controller, which supervises bus activity. A Master which Reads/Writes data to a Slave board, and a Slave interface which simply allows data to be accessed via a Read or Write from a Master.

VME Controller
The VMEbus Controller 'controls' access to the bus. Upon receiving a "Bus Request" signal from a bus Master, the Controller will "Bus Grant" that Master access to the bus. The Controller also handles Interrupts on the bus. When an Interrupt is received on one of the IRQ lines the Controller will process that Interrupt by accessing the Interrupting card, and acknowledge the Interrupt. Only one Controller may reside on the VME bus.

VME Bus-Master
The VMEbus Master Reads and Writes data to or from a Slave board. The Master "Bus Requests" access to the VME bus from the Controller. Once the Controller "Bus Grants" the Master access, the Master drives the Address and Data bus to perform a data transfer to a Slave board. Any number of bus Masters may reside on the VME bus, but only one may have control of the bus at any one time.

VME Bus-Slave
A VMEbus Slave interface simply monitors the Address and Data bus for Reads or Writes sent to it. Once a correctly decoded address is received the Slave will either receive information {for a Write}, or output information onto the Data bus in the case of a Read. The bus Master continues to control the Data bus during either interface. A Slave may also generate Interrupts over any of 7 IRQ lines. The Interrupts are acknowledged by the bus Controller. Any number of Slave boards may reside on the VME bus

The original spec was IEEE 1014-1987 which defined two 3 row P1/P2 connectors, providing a 32 bit Data transfer rate of 40MBytes/second. Revision C allowed 64 bit Data transfers, with the upper 32 data bits being multiplexed onto the address bus once the address cycle was complete (after the address was broadcast) during Block Transfers (BLT). ANSI/VITA 1-1994 termed VME64, increased the data bus width to 64 bits and added a 5 Row P1/P2 connector, and many other features providing transfers of 80MBps.

VITA 1.1-1997, termed VME64x defined the 'z' and 'd' rows of P1 and added the P0 connector. With the back-plane now using the 5 row (160 pin) connectors (increased from the original 3), providing more ground/power pins; an increase in speed of up to 160Mbps was achieved. How ever the 5 row connectors are only required for the 64x enhancement, moving to VME320 (again) only requires the 3 rows (96 pin). VME320 (patented by Arizona Digital, and licensed by Bustronic Corp.) increased the bus speed to 320 MBps on the back-plane.

There are a number of other specifications which increase the data through-put even higher by using the "user defined" P2 pins, the P0 connector or by bringing the data out the front panel. ANSI/VITA 10-1995 termed SKYchannel, uses the P2 connector to transfer data @ 320 Mbytes/sec. P2CI also uses the user defined P2 pins (PCI on the P2 connector). ANSI/VITA 17 termed FPDP (Front Panel Data Port) uses a 32-bit synchronous data bus to transfer data at 160MBytes/sec, using differential PECL over the front panel. ANSI/VITA 5-1994 or Raceway Interlink uses a P2 Backplane daughter card. There are a number of others. Refer to the link "P2 Add-on" bus at the top of the page.

There are two main types of Data transfers on the bus; single cycle, or BLock Transfer {BLT}. A single cycle consists of the Master performing an Address cycle followed by a single Data transfer cycle. A block transfer cycle consists of the Master performing a single Address cycle followed by up to 256 data cycles. A Block Transfer consists of up to a 256 Byte transfers. Block Transfers increase the though-put of the bus by reducing the over head. For 256 bytes only one bus request cycle is required, and only one Address cycle is required.


VME Bus Data Width selection
VMEbus Data Width

During the start of a transfer, the Master will set the Data Transfer Bus [DTB] width using the two Data Strobes [DS0, DS1], Address bit 01 [A01] and bit 02 [A02], and LWORD.
The condition of these lines at the start of a data transfer informs the Slave of the incoming data bus width. VME allowed 32 bit BLock Transfer [BLT].
VME64 added a 64bit Multiplexed BLock Transfer [MBLT] which uses the 32 bit data bus and the 32 bit address bus to transfer data.
Both tables; Extracted from -- VME Interface Board Design Document 1/03/93, Leroy Davis

The VME Address bus width used by the Master is determined by the setting of the Address Modifier [AM] codes.
The graph shows a range of codes used for each address bus width.
The tables does not show the other uses of the AM codes, which include the type of access privilege. A64 uses the full 32 bit address bus and 32 bit data bus [added by VME64].
A40 uses the full 24 bit address bus on J1 and the full 16 bit data bus on J1 [added by VME64]. Extracted from -- VME Interface Board Design Document 1/03/93, Leroy Davis

VME Bus Address Width selection using Address Modifier Codes
VMEbus Address Width

{VMEbus Index}


VME Bus Termination

Passive VME Bus terminations
VMEbus Termination Scheme

Terminations are used on all VMEbus signal lines except for the 'Daisy-Chained' lines. The resistor values used are 330 ohms (from signal line) to +5volts [Pull-up], and 470 ohms (from signal line) to Ground [Pull-down]. The resistor terminations are used at each end of the VMEbus. The voltage presented by the termination is 2.94 volts +/- 10%. The thevenin resistance is equal to 194 ohms (+/-5%). The backplane trace impedance is defined as 100 ohms; however with a fully loaded backplane [with cards installed] the bus impedance is assumed to drop down below 50 ohms. The thevenin termination impedance of 194 ohms is a compromise between allows some reflections and not requiring 50 ohm drivers on the backplane.
Details on Terminations and Reflections is found under this link. Pull-Up resistor calculations are listed on it's own page.

Low voltage terminations for 3.3 volts use 220 ohms (from signal line) to +3.3volts and 1.8K ohms (from signal line) to Ground.

Active termination cost more, but uses much less power; Also see the page on Trace Reflections.
Common Resistor Network termination packages will be either A SIP, DIP or BGA package.
Vendors that Manufacturer Resistor Networks. Styles Resistor Networks

{VMEbus Manufacturers Index}


VME Data Bus Transfer Timing

VME Data Strobe (Valid) timing diagram
VMEbus Strobe Timing Diagram

VME data bus Transfer timing: The Master places data on the Data Transfer Bus [DTB]. The Master then waits a minimum of 35nS before bringing one or both of the Data Strobe(s) [DS] low. The Data Strobe(s) going low indicate to the Slave that the Master has placed valid data on the bus. There is no defined time for the Slave to acquire the data and acknowledge the transfer. How ever once the Slave has latched the data it will bring DTACK low. The Master will then release the Data Strobe(s). Once both of the data strobes are taken high the slave will release DTACK completing the data transfer cycle.
The level of the data strobes during transfer indicate which bytes are accessed. Extracted from -- Interface Board VME Design 1/03/93, Leroy Davis


VME Address Strobe (Valid) timing diagram
VMEbus AS Strobe Timing Diagram

The VMEbus Master takes IACK high and places the address and AM [0-5] codes on the bus.
Once the lines have been valid for 35nS the Master takes the Address Strobe [AS] low to indicate a valid address on the bus.
For Interrupt cycles the IACK lines are driven low. Extracted from -- Interface Board VME Design 1/03/93, Leroy Davis


VMEbus Data transfer cycle
VMEbus Data Timing Diagram

VMEbus Block transfer timing cycle
VMEbus Block Timing Diagram

A VMEbus BLock Transfer [BLT] consists of a single Address cycle followed by up to a 256 Byte Data transfer [in ether 8, 16, or 32 bit segments].
VME64 added the Multiplexed BLock Transfer [MBLT]. MBLT uses all 32 data bits and all 32 address bits to transfer 64 data bits at once over the bus.


VME Bus request cycle

VME Bus Access Timing Diagram

The (up-coming) Master makes a Bus Request, the Controller gives a Bus Grant, then asserts Bus Busy.

The data charts above relate to rev. 'C' and 'D' of the VME spec [which was replaced by VME64]. The newer versions of the spec added two new enhancements, termed 2eVME and 2eSST.

2eVME which means "2 Edges", increased transfer speed by reducing data transfers from 4 edges to 2. Instead of the source taking DAV low [data valid], the slave taking DTACK low [data accepted], than the source bringing DAV high, and waiting for the slave to take DTACK high which would allow a new cycle to begin. The new process transfers data on each edge of DAV, effectively doubling the data transfer rate. So DAV going low would allow one data transfer, waiting for a low on DTACK, than DAV going high would allow another data transfer.

2eSST which means "2 Edges, Source Synchronous Transfer"; adds to 2eVME, 2eSST does not wait for an acknowledgment (during data phases). This means that the VME hand-shake does not exist. 2eSST transfers data at the Masters rate and is not slowed by the slaves ability to accept data. DS1 is used as the clock when transferring data, and DTACK is used as the clock when reading data.

{VMEbus Index}


VMEbus Card Dimensions [Form Factors] -Sizes-

IEEE 1101.1 Base Document for Mechanics ~ Defines 3U/6U/9U (high) x 100/160/220/280/340/400mm (Long) cards
IEEE 1101.10 Mechanics for VME Boards and Subracks
IEEE 1101.11 Mechanics for Rear Transition Modules

Three card heights are allowed with VME; 3U, 6U, or 9U; a single slot card is 6T wide. Length is either 160mm or 340mm (Norm)
Height is given in 'U' [1U = 43.60mm], Length is given in 'mm', Width is given in 'T' or HP [1HP = 5.08mm [HP: Horizontal Pitch]; Card sizes listed below are one slot or 6T wide
A size CCA dimensions = 3U x 160mm. A 3U Printed Wiring Board [PWB] is 100mm high.
B size CCA dimensions = 6U x 160mm. A 6U Printed Wiring Board [PWB] is 233mm high.
C size CCA dimensions = 6U x 340mm, ... {H x L x W {@ width=6T}
D size CCA dimensions = 9U x 340mm. A 9U Printed Wiring Board [PWB] is 360mm high.
A, B, C, and D are VXI terms. VME normally only references 3U or 6U [dimensions] by a length.




The board thickness for VME cards is 0.063 +/- 0.008 inchs [1.6mm +/- 0.2mm] Thicker or thinner CCAs may not fit in the card guides correctly.
How ever an 0.90 board may work if you mill down the top and bottom [2.5mm] of the card to 0.63 so it fits in the card guides.

3U, 6U, 9U Card sizes Basic Board Size - 3D

VME Cards [Dimensions] Shape,{Euro Format}
VMEbus Board Formats

'C' Size 340mm x 233mm {6U} Detailed Mechanical [Dimensions] Form Factor

'D' Size 340mm x 366mm {9U} Detailed Mechanical [Dimensions] Form Factor

VME OEM Card Vendors, products list

{VMEbus Index}


VMEbus Standards and Specifications

VITA {VMEbus International Trade Association}

IEEE; Institute of Electrical and Electronic Engineers, Inc. [www.ieee.org]

IEEE 1014-1987{VME} The original VME Spec. {3 row P1/P2, 32 bit Xfers, 64 w/ the address bus MUXed} @ 40MBytes/second [Replaced by ANSI/VITA 1-1994; VME64]
ANSI/VITA 1-1994 {VME64} added 5 Row P1/P2...many other features
VITA 1.1-1997 {VME64x; VME64 Extensions} which defined the 'z' and 'd' row of P1, added P0 @ 80MBytes/second
VITA 1.3-1997 Added 9U x 400mm
IEEE 1101.1 Mechanical Specifications
VITA 1.5 SST Source Synchronous Transfer using ETL (ABTE) devices for the VME64 bus
VITA 4-1997 Added IP Modules
VITA 4.1-1997 Added IP Module mapping to VME64x
ANSI/VITA 5.1-1994{Raceway Interlink} P2 Backplane Interconnect scheme
VITA 6-1994 SCSA
ANSI/VITA 17 -1998{FPDP; Front Panel Data Port} 32-bit synchronous front panel data bus @ 160MBytes/sec, differential PECL
ANSI/VITA 10-1995{SKYchannel} P2 used to transfer data @ 320 Mbytes/sec
VITA 12-1996 M-Modules Mezzanine
VITA 18-1997 VME Bus Pin Assignments for Military {MIL-STD-1389} Format-E Boards and Backplanes
VITA 26-1998 Myrinet-on-VME
VITA 30.2: Separable Power Connectors [pinout for IEC 60603-2 Type M Connector]
VITA 31 Serial I/O on 2mm Connectors
VITA 31.1: Gigabit Ethernet [GbE ]on VME64x P0
VITA 32 Processor PMC (PPMC)
VITA 35-2000 PMC Mapping to VME64 P0/P2
VITA 39: PCI-X for PMC and Processor PMC (PMC-X)
VITA 41: VMEbus Switched Serial Standard (VXS)
VITA 42: Express Mezzanine Card (XMC)
VITA 46: VPX
VITA 27 {P2CI} PCI on P2 VME Compatible Interface [Cancelled]
VME320: 320 Mbytes/sec back-plane. Patented by Arizona Digital, increased the bus speed to 320 MBps
ISO/IEC 60821 or ISO/IEC 821 [the old number] is the same as IEEE 1014-1987
ISO/IEC 15776 is the same as ANSI/VITA 1 1994

Speed Increases with Standard updates;
VME32: 40MB/s
VME64: 80MB/s [same speed for VME64x]
VME 2eSST: 320MB/s
VXS: 3GB/s [30GB/s]

{VMEbus Index}


VME Bus Interface IC Manufacturers

The VME bus uses normal TTL devices.
The VME64-ETL specification uses the ABTE (Advanced - BiCMOS - Technology - Enhanced Transceiver) Logic family.
The VMEbus signal types are listed below:
Open collector signals which require Open Collector drivers and receivers:
ACFail, BBSY, BERR, DTACK, IACK, SERDAT, SYSFAIL, SYSRESET, [IRQ1 - IRQ7], and [BR0 - BR3].
Three-State signals which require 3-State drivers and receivers:
AS, DS0, DS1, DTACK, RETRY, IACK, LWORD, WRITE, [AM0 - AM5], [A01 - A31], and [D00 - D31].
Totem-Pole signals which require Totem-Pole drivers and receivers:
BCLR, SYSCLK, SERCLK, IACKIN, IACKOUT, [BG0IN - BG3IN], [BG0OUT - BG3OUT].




Cypress *These devices are Obsolete and not recommended for new designs*
{VME Controllers(Master: 32-bit VIC068A / 64-bit VIC64), (Slave: CY7C960 / CY7C961)}
{VME I/O CY7C964 bus interface - used with either the VIC chips or the 960 series}
{5962-92010: CMOS VMEBus Interface Controller; VIC068A; Pin grid array & Flat Pack.}

Fairchild Semiconductor Corp. {VME320 8-Bit Registered Bus Transceiver ICs}

Inicore Inc. {VMEbus Master Slave Controller, VME to local bus bridge. IP Core Vendor}

National Semiconductor Corp {54/74ETL16245, VME 16 bit transceiver Incident Wave Switching IC Manufacturer}

Texas Instruments 'TI' {74VMEH22501, VMEbus 8 bit transceiver/2eSST, also ABTE16245 ICs}

Tundra Semiconductor [IDT] {VME64 Bus Controller ICs-VME Bridges to PCI/Local Bus, PCI-X to 2eSST VME bridge chip TSI148 "Tempe"}

IC Manufacturers {All other chip types}

{VME Bus Index}


VMEbus System Block Diagrams

VME Slave Interface - Top Level


VME Bus Pin-Out

VME boards are produced with either 96 pin or 160 pin J1/J2 connectors.
Under the latest bus specification (which added the 160 pin connector) either connector may be used (but I believe both have to be the same type).

P1 pin out {IEEE 1014-1987}; VMEbus, {96 Pin Connectors Pin-Out: 3 Rows x 32 Pins}

P2 pin out {IEEE 1014-1987}; VMEbus, {96 Pin Connectors Pin-Out: 3 Rows x 32 Pins}

P1 pin out {ANSI/VITA 1-1994}; VME64 bus, {160 Pin Connector Pin-Out: 5 Rows x 32 Pins}

P2 pin out {ANSI/VITA 1-1994}; VME64 bus, {160 Pin Connector Pin-Out: 5 Rows x 32 Pins}

P0 {ANSI/VITA 1-1994}, {95 Pin Connectors: 5 Rows x 19 Pins}
{Pinout is only defined for PMC, Myrinet, ATM I/O and GbE}

SEM E {VITA 18-1997}
VME Bus Pin Assignments for Military {MIL-STD-1389} Format-E Boards and Backplanes

{VME Bus Index}


VME Bus Connector Manufacturers

There are a number of different connector types used with the VMEbus
P1 and P2 are 96 pin DIN (41612, Type C) 3 rows x 32 pins [Pitch 2.54mm (.100")] @ IEEE 1014-1987; [VME]
P1 and P2 are 160 pin DIN (41612, Type C Expanded) 5 rows x 32 pins [Pitch 2.54mm (.100")] @ ANSI/VITA 1-1994; [VME64]
P1 connectors may also come with an Auto Bus Grant [ABG] option which is an automatic [mechanical] switching capability built-in to auto jumper the slot

P2 Split DIN / RF Coax (DIN 41612 Type M) DIN + Coax @ 78 + 2, 60 + 4, 42 + 6, 24 + 8
P0 95 pin 2mm 5 rows x 19 pins (IEC 1076-4-101), PCI Style @ VITA 1.1-1997

Infiniband [VITA 31 VME64 P0 Backplane Interconnect] 2mm Twin-ax uses the Gigabit Ethernet HSSDC Connector and Cable (HSSDC - High Speed Serial Data Connector)
FPDP [ANSI/VITA 17 {FPDP; Front Panel Data Port}] 80 conductor (20 pins x 4 rows), 25mil pitch

The class of connectors determines the number of insertions it's [Mechanical Endurance] designed to handle per DIN 41612.
Class 1: 500 mating cycles
Class 2: 400 mating cycles
Class 3: 50 mating cycles

VME 3row/5 row DIN Connector Dimensions

The connector class is defined by the DIN standard, and is not defined by the VME standard.




2E SysCom Inc. {Type B/C Signal / Type D/F/G/H15/H11/M VME Power connectors}

3M {3x32 Row DIN 41612-5x19 row 95 pin IESC 1076-4-101 - FPDP Connector}

Advanced-Connectek INC. 'ACON' {VME connector}

AVX Corp. {DIN 41612 Type C/C Expanded 3x32 Row-DIN 41612 Type M -Split DIN/Coax 78 + 2 / 60 + 4 / 42 + 6 / 24 + 8 / 4 + 10}

Conec {DIN VME 41612/41617 VME connector Manufacturer}

ECS Inc. {VME DIN 41612 connector Manufacturer}

DINTEK {VME Press Fit connectors}

ept {DIN 41612 VME Connectors/Type B, C, D, E, F, M (Split DIN/Coax) 24 + 8, R}

Erni {VME 3x32 Row-DIN 41612 Type C-Split DIN/Coax Type M 78 + 2 / 60 + 4 / 42 + 6 / 24 + 8-CPCI 2mm type}

Essen Deinki {DIN 41612 Euro/Reverse Euro Connector Manufacturer}

FCI {VME DIN 41612/Split DIN/Coax RF Connectors}

Harting {DIN 41612 - VME 5 and VME 3 Row Type C connectors}

Hirose Electronic {VME DIN 3/5 Row-DIN 41612/IEC 603-2/DIN 41612M - High-frequency coaxial hybrid connector}

lmi Components {DIN 41612 Type D/E/F VME Connector Manufacturer}

Methode Electronics {VME Connectors}

Molex {VME 3x32 Row-DIN 41612 Type C-Split DIN/Coax Type M78 + 2 / 60 + 4 / 42 + 6 / 24 + 8}

Phoenix {DIN41612 VME connectors, PKZ style connectors}

Tyco Electronics {3x32 Row-DIN 41612 Type C-Split DIN/Coax Type M 78 + 2 / 60 + 4 / 42 + 6 / 24 + 8 - CPCI 2mm type}

Y-connect {VME 3x32 Row-Right Angle/Vertical DIN 41612 Type}

Winchester Electronics {Hybrid VME DIN Multi-purpose Connector (Coax) Manufacturer}

DIN 41612 Size [Standard or reverse Pinout]
DIN 41612 Size
B
Q
C
R
CD
RD
E
TE
M
Orientation Standard Inverse Standard Inverse Standard Inverse Standard Inverse Standard
Max Number of Contacts
64
96
128
160
78
Contact Row Designation
ab
ab
abc
abc
abcd
abcd
abcde
abcde
abc

2mm ['Hard Metric'; IEC 1076-4-101] connector vendor sites are listed on the cPCI page
cPCI 2mm connectors mating distances [12.50mm] matches the 96 pin DIN 41612 connectors used with other EuroCard packaging [IEC 273 or IEEE 1101, 1101.10], like VMEbus.
FutureBus connectors, which also use 2mm style has a mating distance of 10mm, and is not compatible with cPCI connectors.

VME cards may either use normal soldered connectors or press-fit connectors.
Press-fit connectors or Compliant Pin Connectors do not need to be soldered to the board; however you may want to bolt them to the PWB.

{VME Manufacturer Index}


VME Chassis Information

A VME Chassis will be between 1 and 21 slots (the maximum).
Care should be taken producing a 21 slot chassis, with the addition of slide rails the width may exceed a standard 19" [EIA-310] rack.
So the practical limit is 20 slots for a chassis mounted in a 19" rack. The term Crate may also be used to indicate a VME chassis.

The [VMEbus] chassis may except 3U cards, or 3U and 6U cards, and now 9U cards. The chassis may have a separate card cage to handle the 3U cards.
The chassis only need provide the P1 side of the back plane when only 3U cards are used. 6U cards require both P1 and P2, and 9U would require the P1, P2, and P3.
A P0 connector (between P1 and P2) for 6U cards may also be provided. Regardless of the size of the card the chassis will accept (3U, 6U, or 9U) all the slots are on .8" centers

VME32 provided a +5volt,and +/-12volt supply; VME64 added a 3.3volt supply. The 5volt supply should provide only 50mV of ripple.
No currently produced power supply meets 50mV, I've seen notes on the web indicating an attempt to update this number.

The VME chassis dimensions will vary depending on the size and number of VME cards required.
The dimensions of a VME chassis would also be effected by the size of power supply used, number of fans, I/O connectors, or rack size.
Companies which produce VME Chassis may be found on the VMEbus Chassis manufacturers page A vendor and VME products listing.

Companies which produce Racks may be found on the Rack manufacturers page, a vendor and products listing.
There is no VME Rack, and no specification that defines a VME Rack.
Insure that the VME chassis fits in the Rack you have, or specify a Rack that will accommodate the size of the VME chassis.
A rack with a 19 inch aperture is common, as well as a 19 inch wide VME chassis.

VME backplanes will always consist of a J1 backplane. Except for the daisy-chained lines all signals on rows A, B, and C of J1 must be bused.
The J1 connector may be either a 3-row (x32) 96-pin or a 5-row (x32) 160-pin connector.

A VME backplane may also have a J2 backplane (in addition to J1).
The J2 backplane may be a separate PWB located just below the J1 backplane or be a monolithic backplane containing both J1 and J2.
All signals on row B of J2 must be bused. The J2 connector may be either a 3-row (x32) 96-pin or a 5-row (x32) 160-pin connector.

The VMEbus backplane may have between 1 and 21 slots. The length of any VME backplane is [number of slots] x [20.32mm].
The height of J1 (or separate J2) backplane is 130mm. A monolithic J1/J2 backplane will be 160mm.


There are a number of considerations to account for when designing a VME chassis.
A successful VME chassis design is more than just a VME backplane in a 19 inch rack mount-able chassis.
So, there's a section of pages covering designing a VME Equipment Chassis [Writing a VME requirements document for a chassis vendor].

How to spec out an equipment chassis; VME Chassis Design Considerations [VME chassis suggestions and pitfalls].

Companies which produce VME Backplanes may be found on the VMEbus Backplane manufacturers page. A VME vendor and products listing.

{VME bus Manufacturer Index}


Topic Navigation: Engineering Home > Interface Buses > Embedded Backplane Buses > VMEbus Description.


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