Rabbit OP7100 User Manual download pdf (Page 4)

The Smart Screen’s expandable memory,

which supports up to 512K of SRAM,

stores up to 30 special point configura-

tions. “These configurations are defined

by the user, and they can be saved as

individual files and then stored and

retrieved via the connection to a PC,”

says Hanson. “So the number

of different sharpening routines is

virtually limitless.”

High Interest Rates

Initial sales and orders indicate the

XPS-16 is generating a lot of interest

among large manufacturers and the

service industry, thanks in part to

Z•World’s smart touchscreen. “This is a

brand-new technology—nobody else

comes close to what we’re doing with

the XPS-16,” says Varney. “And one of

the main selling features of the product

is the interface.”

The Smart Screen’s easy operation, com-

bined with the sharpener’s precision

cutting ability, ensure fast, consistent

results every time. “When customers

select the XPS-16, they can be sure

they’re getting unmatched accuracy and

flexibility—without the high price tag,”

says Varney.

Many already want to know if Darex is

planning to develop other sharpening

equipment with the same automated

design features that distinguish the

XPS-16. “Since we’ve come out with the

inexpensive CNC drill sharpener, cus-

tomers are asking us to look at applying

the same technology to other types of

sharpeners,” says Sobolik. “We’re cer-

tainly considering the possibilities, and

with the early success of the XPS-16, it

makes perfect sense to springboard off

the same platform as much as possible.”

www.darex.com

800.547.0222

External I/O Feature of the Rabbit 2000 Microprocessor

The Rabbit 2000’s external I/O feature allows the user to access up to 64K

of “external” I/O space. The I/O space is divided into eight 8K pages based

on the upper three bits of the specified address. These three bits are decoded

by the processor and are used to select which bit of parallel port E is to be used

as the I/O strobe.

The bits of parallel port E can be individually enabled to act as I/O strobes. Each

strobe/bit accesses an 8K page using the lower 13 address bits of the Rabbit 2000

address bus. The I/O devices also connect to the 8-bit data bus.

The bits of parallel port E are enabled as I/O strobes by using PEFR. Each bit of

PEFR controls the operation of the corresponding bit of port E. A “0” value causes

the bit to be used as a parallel I/O bit. A “1” value causes the bit to be used as an

I/O strobe. The appropriate PEDDR bits should also be set so that the selected pins

are programmed to be outputs. Also, since the bits of port E are initialized as inputs

when the processor is reset, you should install a pull-up resistor on each pin that

will be used as an I/O strobe.

The specific operation of the I/O strobe is controlled by IBnCR where “n” represents

the appropriate bit in port E. The IBnCR allows the bit of port E to act as chip select

pulse, write pulse, read pulse, or the OR of write and read pulses—all low true. Also,

IBnCR allows the programmer to select the number of wait states basically controlling

the width of the selected pulse type. One of the bits in the register is also a write

enable. If this bit is not set, the processor will not generate the /IOWR signal.

The other signals to be used are /IOWR, /IORD, and /BUFEN. /IOWR is pulsed low

for a write operation. /IORD is pulsed low for a read operation. /BUFEN is pulsed

low in either case. The timing for these signals is detailed in the Rabbit 2000

Microprocessor User’s Manual.

It is recommended that if there is the possibility of a relatively heavy load being

placed on either bus, then bus drivers and bus transceivers should be used. The bus

drivers would buffer the address bus, while the bus transceivers would buffer the

data bus. The transceiver operation must be such that it is normally transmitting the

data bus to the external I/O devices—only receiving when an I/O read is taking

place. To do this, either /IORD or /IOWR must be used to control the direction of

the transceiver. If /BUFEN is also used to enable the devices, then pull-up or pull-

down resistors must be placed on the “outboard” side of the devices to ensure that

the external I/O device inputs are never floating.

continued from page 3

Rabbit 2000™

I/O Device

D0...D7

A0...(A12)

/IOWR

/IORD

PEn

D0...D7

A0...(An)

/WR

/RD

/CS

In Control • Fall 2001 • www.zworld.com

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Rabbit OP7100 User Manual Page 4

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