Ciprico Rimfire 3880 manual

Models: Rimfire 3880

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Chapter 7 Board-control Commands

Page 7 - 16

 

General Options (07H)

Note

The adapter will enforce a minimum burst size equal to the transfer width. The adapter will also enforce a maximum burst for Block Mode transfers, in order to ensure adherence to the VME specification— rules 2.12 and 2.75— related to address boundaries.

Bus Throttle

The bus throttle control allows you to regulate the flow of SCSI data on the VMEbus. The flow of data is regulated by limiting the number of bytes that the adapter is allowed to transfer each time it acquires the bus. The adapter transfers the data in bursts. You may specify the number of bytes that the adapter transfers in a burst by placing the appropriate value in the Bus Throttle field.

The number of bytes in a burst is expressed as a power of 2. The possible values are 0 though 0BH.

The table below translates the Bus Throttle field values into number of bytes per burst.

The default setting for this field is 0BH, 2048 bytes per burst.

Value

Represents

Number of Bytes per Burst

00H

20

1

01H

21

2

02H

22

4

03H

23

8

04H

24

16

05H

25

32

06H

26

64

07H

27

128

08H

28

256

09H

29

512

0AH

210

1024

0BH

211

2048

 

 

 

Table 72: Bus Throttle Field Values

Select Flags

The Select Flags are used to determine several operating factors for the RF3880 adapter. Use of Block Mode transfers by the adapter is affected by Select Flags.

Other factors pertain to the SCSI bus: parity checking and disconnect/ reconnect.

The format of the Select Flags byte is as follows:

BITS

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

0

0

0

0

X

BMT

PAR

DIS

 

 

 

 

 

 

 

 

Table 73: Select Flags Byte

DIS Disconnect/Reconnect - With this bit you are able to select whether the RF3880 adapter will allow peripherals to disconnect from the SCSI bus while performing a command.

0 Disallow Disconnect/Reconnect.

1 Allow Disconnect/Reconnect.

The default value for this bit is one — allow disconnects on all commands.

21020285 D

User’s Guide

Page 140
Image 140
Ciprico Rimfire 3880 manual