AM79C960KCW datasheet(46/127 Pages) AMD

46 / 127 page

P R E L I M I N A R Y

AMD

1-388

Am79C960

General Purpose Serial Interface (GPSI)

The PCnet-ISA controller contains a General Purpose

Serial Interface (GPSI) designed for testing the digital

portions of the chip. The MENDEC, AUI, and twisted

pair interface are by-passed once the device is set up in

the special “test mode” for accessing the GPSI func-

tions. Although this access is intended only for testing

the device, some users may find the non-encoded data

functions useful in some special applications. Note,

however, that the GPSI functions can be accessed only

when the PCnet-ISA devices operate as a bus master.

The PCnet-ISA GPSI signals are consistent with the

LANCE digital serial interface. Since the GPSI functions

can be accessed only through a special test mode, ex-

pect some loss of functionality to the device when the

GPSI is invoked. The AUI and 10BASE-T analog inter-

faces are disabled along with the internal MENDEC

logic. The LA (unlatched address) pins are removed and

become the GPSI signals, therefore, only 20 bits of ad-

dress space is available. The table below shows the

GPSI pin configuration:

To invoke the GPSI signals, follow the procedure below:

1. After reset or I/O read of Reset Address, write 10b

to PORTSEL bits in CSR15.

2. Set the ENTST bit in CSR4

3. Set the GPSIEN bit in CSR124 (see note below)

(The pins LA17–LA23 will change function after the

completion of the above three steps.)

4. Clear the ENTST bit in CSR4

5. Clear both media select bits in ISACSR2

6. Define the PORTSEL bits in the MODE register

(CSR15) to be 10b to define GPSI port. The

MODE register image is in the initialization block.

Note:

LA pins will be tristated before writing to

CORETST bit. After writing to GPSIEN, LA[17–21] will

be inputs, LA[22–23] will be outputs.

Table: GPSI Pin Configurations

LANCE/

PCnet-ISA

GPSI

C-LANCE

GPSI

PCnet-ISA Normal

Function

I/O Type

GPSI Pin

Pin Function

Number

Pin Function

Receive Data

RXDAT

LA17

Receive Clock

RCLK

SRDCLK

LA18

Receive Carrier Sense

RENA

RXCRS

LA19

Collision

CLSN

LA20

Transmit Clock

TCLK

STDCLK

LA21

Transmit Enable

TENA

TXEN

LA22

Transmit Data

TXDAT

LA23

Note: The GPSI function is only available in the Bus Master mode of operation.

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