AM79C970 datasheet(119/168 Pages) AMD

119 / 168 page

AMD

P R E L I M I N A R Y

1-986

Am79C970

12–5

RES

Reserved locations. Written as

ZERO, read as undefined.

EEN

EEPROM port enable. When this

bit is set to a one, it causes the

values of ECS, ESK and EDI to

be driven onto the EECS, EESK

and EEDI pins, respectively. If

EEN=0 and no EEPROM read

function is currently active, then

EECS will be driven LOW. When

EEN=0 and no EEPROM read

function is currently active, EESK

and EEDI pins will be driven by

the LED registers BCR5 and

BCR4, respectively.

EEN is set to ZERO by H_RE-

SET and is unaffected by the

S_RESET or STOP bit.

RES

Reserved location. Written as

ZERO and read as undefined.

ECS

EEPROM Chip Select. This bit is

used to control the value of the

EECS pin of the Microwire inter-

face when the EEN bit is set to

ONE and the PREAD bit is set to

ZERO. If EEN = 1 and PREAD =

0 and ECS is set to a ONE, then

the EECS pin will be forced to a

HIGH level at the rising edge of

the next CLK following bit pro-

gramming. If EEN = 1 and

PREAD = 0 and ECS is set to a

ZERO, then the EECS pin will be

forced to a LOW level at the rising

edge of the next CLK following bit

programming. ECS has no effect

on the output value of the EECS

pin unless the PREAD bit is set to

ZERO and the EEN bit is set to

ONE.

ECS is set to ZERO by H_RE-

SET and is not affected by

S_RESET or STOP.

ESK

EEPROM Serial Clock. This bit

and the EDI/EDO bit are used to

control

host

access

the

EEPROM. Values programmed

to this bit are placed onto the

EESK pin at the rising edge of the

next CLK following bit program-

ming, except when the PREAD

bit is set to ONE or the EEN bit is

set to ZERO. If both the ESK bit

and the EDI/EDO bit values are

changed during one BCR19 write

operation, while EEN = 1, then

setup and hold times of the EEDI

pin value with respect to the

EESK signal edge are not guar-

anteed.

ESK has no effect on the EESK

pin unless the PREAD bit is set to

ZERO and the EEN bit is set to

ONE.

ESK is reset to ONE by H_RE-

SET and is not affected by

S_RESET or STOP.

Table 11. EEPROM Port Enable

PREAD or

Auto Read

RST Pin

in Progress

EEN

EECS

EESK

EEDI

Low

High

Active

High

From ECS

From ESK Bit

From EDI Bit

Bit of BCR19

of BCR19

High

LED1

LNKST

AM79C970 Datasheet(PDF) 119 Page - Advanced Micro Devices

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