EV-2 datasheet(13/44 Pages) CIRRUS

13 / 44 page

CobraNet™ EV-2

Rev. 2.1

Port 3: See Table 5 on page 13.

Interfacing the Microcontroller to the CM

Please refer to the EV-2 schematic, found in Appendix D for information regarding interfacing

to the CM.

The CM has a host interface that allows a host processor (such as an 8051 microcontroller)

to interface to the DSP on the CM. From a hardware perspective the interface to the CM-1

and CM-2 is almost the same,. The host interface signals are a data strobe signal, HDS#; a

read/write line, HRW, an 8-bit bi-directional data bus, HD0-HD7, and three address lines,

HA0-HA2 on the CM-1 and four address lines, HA0-HA3 on the CM-2. The HEN# line has

been configured by the CobraNet software to be ignored or seen as a logic low. Given this

host configuration, the interface of the microcontroller to the CM host port is straightforward.

In addition to the above signals there are two more, HACK# and HREQ# which can be used

as flags to indicate a state change on the CM.

With regard to the CM-1 which uses a Motorola DSP56303, care must be taken with the

timing of HDS# and HWR. Motorola's timing specifications for the DSP56303 host port in a

non-multiplexed, single data strobe mode requires a set up time from the falling edge of

HWR# to the falling edge of HDS# of 4.7ns and the hold time from the rising edge of HDS# to

the rising edge of HWR# of 3.3ns. The pulse of the HDS# signal must be wholly within the

pulse of the HWR# signal with the constraints stated above. Please refer to Motorola's

DSP56303 Technical Data sheet for complete information regarding timing and interface

issues.

This

available

for

download

from

the

Motorola

web

site

http://www.freescale.com.

Bit #

Name of Signal

I/O

Description

RXD

RS232 serial port receive signal.

TXD

RS232 serial port transmit signal

HREQ#

Connected to the CM module host

request signal. See CobraNet

Technical Datasheet for a com-

plete description of this signal.

HACK#

Connected to the CM module host

acknowledge signal. See Cobra-

Net Technical Datasheet for a

complete description of this signal.

May be used as an interrupt

request on the microcontroller.

Watchdog

Watchdog signal from the CM

MCU_P35

I/O

Connected to SCI_CLK via the

FPGA. Also used to detect sample

rate.

WR#

Microcontroller write signal.

RD#

Microcontroller read signal.

Table 5: Port 3 Signal Descriptions

EV-2 Datasheet(PDF) 13 Page - Cirrus Logic

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