AM79C960KCW datasheet(62/127 Pages) AMD

62 / 127 page

P R E L I M I N A R Y

AMD

1-404

Am79C960

DXMT2PD

Disable

Transmit

Two

Part

Deferral. If DXMT2PD is set,

Transmit Two Part Deferral will

be disabled.

DXMT2PD is cleared by RESET

and is not affected by STOP.

EMBA

Enable

Modified

Back-off

Algorithm. If EMBA is set, a modi-

fied

back-off

algorithm

implemented.

Read/Write accessible. EMBA is

cleared by RESET and is not af-

fected by STOP.

2-0

RES

Reserved locations. Written as

zero and read as undefined.

CSR4: Test and Features Control

Bit

Name

Description

ENTST

Enable Test Mode operation.

When ENTST is set, writing to

test mode registers CSR124 and

CSR126 is allowed, and other

abled. In order to set ENTST, it

must be written with a “1” during

the first write access to CSR4

after RESET. Once a “0” is writ-

ten to this bit location, ENTST

cannot be set until after the

PCnet-ISA controller is reset.

ENTST is cleared by RESET.

DMAPLUS

When DMAPLUS = “1” , the burst

transaction counter in CSR80 is

disabled. If DMAPLUS = “0”, the

burst

transaction

counter

enabled.

DMA-PLUS

cleared

RESET.

TIMER

Timer Enable Register. If TIMER

is set, the Bus Timer Register,

CSR82, is enabled. If TIMER is

set, CSR82 must be written with

a value. If TIMER is cleared, the

Bus Timer Register is disabled.

TIMER is cleared by RESET.

DPOLL

Disable

Transmit

Polling.

DPOLL is set, the Buffer Man-

agement

Unit

will

disable

transmit

polling.

Likewise,

DPOLL is cleared, automatic

transmit polling is enabled. If

DPOLL is set, TDMD bit in CSR0

must be periodically set in order

to initiate a manual poll of a trans-

mit descriptor. Transmit descrip-

tor polling will not take place if

TXON is reset.

DPOLL is cleared by RESET.

APAD_XMT

Auto Pad Transmit. When set,

APAD_XMT enables the auto-

matic padding feature. Transmit

frames will be padded to extend

them to 64 bytes, including FCS.

The FCS is calculated for the en-

tire frame (including pad) and

appended after the pad field.

APAD_XMT will override the pro-

gramming of the DXMTFCS bit

(CSR15.3).

APAD_ XMT is reset by activa-

tion of the RESET pin.

10 ASTRP_RCV

ASTRP_RCV enables the auto-

matic pad stripping feature. The

pad and FCS fields will be

stripped from receive frames and

not placed in the FIFO.

ASTRP_ RCV is reset by activa-

tion of the RESET pin.

MFCO

Missed Frame Counter Overflow

Interrupt.

This

bit

indicates

the

MFC

(CSR112) has overflowed. Can

be cleared by writing a “1” to this

bit. Also cleared by RESET or

setting the STOP bit. Writing a “0”

has no effect.

MFCOM

Missed Frame Counter Overflow

Mask.

If MFCOM is set, MFCO will not

set INTR in CSR0.

MFCOM is set by Reset and is

not affected by STOP.

7-6

RES

Reserved locations. Read and

written as zero.

RCVCCO

Receive Collision Counter Over-

flow.

This bit indicates the Receive

Collision Counter (CSR114) has

overflowed. It can be cleared by

writing a 1 to this bit. Also cleared

by RESET or setting the STOP

bit. Writing a 0 has no effect.

RCVCCOM

Receive Collision Counter Over-

flow Mask.

If RCVCCOM is set, RCVCCO

will not set INTR in CSR0.

RCVCCOM is set by RESET and

is not affected by STOP.

TXSTRT

Transmit Start status is set when-

ever PCnet-ISA controller begins

trans- mission of a frame.

When TXSTRT is set, IRQ is as-

serted if IENA = 1 and the mask

bit TXSTRTM (CSR4.2) is clear.

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