Exabyte EXB-8205 Instruções de Operação descarregar pdf (Página 57)

100

101

The format of the Synchronous Data Transfer Request message is as

follows:

Bit

Byte

76543210

0000000001

01 Extended Message Length

02 Extended Message Code

03 Transfer Period

04 REQ/ACK Offset

Byte 00 - Extended Message ThevalidvaluefortheExtended

Message field is 01h, indicating that this is an extended message

that contains multiple bytes.

Byte 01 - Extended Message Length The valid value for the

Extended Message Length field is 03h, indicating that there are

three additional message bytes to be transferred, not including

this byte.

Byte 02 - Extended Message Code The Extended Message Code

byte identifies the specific extended message being sent. The valid

value for this byte is 01h, indicating that the Extended message is

a Synchronous Data Transfer Request.

Byte 03 - Transfer Period This byte identifies the minimum time

allowed between leading edges of successive REQ pulses and

ACK pulses for successful reception of data. The value represents

the number of 4-nanosecond increments allowed for the

synchronous transfer period. The CTS supports a minimum of 50

increments or 200 nanoseconds for the minimum synchronous

transfer period.

Byte 04 - REQ/ACK Offset This byte identifies the maximum

number of REQ pulses that can be outstanding before the leading

edge of the corresponding ACK is received by the CTS. The CTS

allows up to 12 outstanding REQ pulses.

May 1994 EXB-8205 and EXB-8505

(Standard and XL)

2-17

2 SCSI Communication

1 2 ... 52 53 54 55 56 57 58 59 60 61 62 ... 445 446

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Exabyte EXB-8205 Instruções de Operação Página 57

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