National Instruments Printer Accessories 320030-01 用户手册

VMEbus Address:

Base Address + 05 (hex)

Attributes:

Read/Write, Internal to DMAC

7

6

5

4

3

2

1

0

DIR

0

SIZE

CHN

REQG

R/W

The Operation Control Register (OCR) is an operation-oriented register.

7r/w

DIR

Direction Bit

The Direction bit specifies the direction of the transfer, to or from
VMEbus memory :

0

=

Transfer from memory to device

1

=

Transfer from device to memory

In GPIB applications, 0 indicates transfers from memory to GPIB and
1 indicates transfers from GPIB to memory.

6r/w

0

Reserved Bit

Write zero to this bit.

5-4r/w

SIZE

Size Bits 5 through 4

The Size bits indicate the size of the data transfer.  For the GPIB-1014
GPIB transfers, the size is always byte 00.  For memory-to-memory
transfers, the size can be byte, word, or long-word.

00 =

Byte (8 bits)

01 =

Word (16 bits)

10 =

Long-word (32 bits)

11 =

(undefined, reserved)

3-2r/w

CHN

Chain Bits 3 through 2

The Chain bits are used to indicate what type of chaining, if any, is
used:

00 =

Chain operation is disabled

01 =

(undefined, reserved)