P R E L I M I N A R Y
AMD
165
Am79C965
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, re-
spectively. See Table 52.
EEN
is
set
to
ZERO
by
H_RESET and is unaffected by
S_RESET or STOP.
3
EBUSY
EEPROM BUSY. This bit con-
trols the value of the SHFBUSY
pin of the PCnet-32 controller
when the EEN bit is set to ONE
and the PREAD bit is set to
ZERO. This bit is used to indicate
to external EEPROM-program-
mable logic that an EEPROM ac-
cess is occurring.
When user programming of the
EEPROM is desired through the
BCR19 EEPROM Port, then
EBUSY should be set to ONE
before EEN is set to ONE in
systems where EEPROM-pro-
grammable external logic exists.
At the end of the EEPROM pro-
gramming
operation,
EBUSY
should either remain set at ONE
until after EEN is set to ZERO, or
the user may reset EBUSY to
ZERO with EEN = 1 immediately
following a read of EEPROM
byte locations 35 and 36, which
should be the last accesses per-
formed during BCR19 accesses
to the EEPROM. A programmed
PREAD operation following the
BCR19 EEPROM programming
accesses
will
cause
the
SHFBUSY pin to become LOW if
the
EEPROM
checksum
is
verified.
EBUSY has no effect on the out-
put value of the SHFBUSY pin
unless the PREAD bit is set to
ZERO and the EEN bit is set to
ONE.
EBUSY is set to ZERO by
H_RESET and is unaffected by
S_RESET or STOP.
2
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 BCLK following bit
programming. 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 BCLK 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_RESET and is unaffected by
S_RESET or STOP.
1
ESK
EEPROM Serial Clock. This bit
and the EDI/EDO bit are used to
control
host
access
to
the
EEPROM. Values programmed
to this bit are placed onto the
EESK pin at the rising edge of the
next BCLK 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
guaranteed.
Table 52. EEPROM Enable
PREAD or
Reset
Auto Read in
Pin
Progress
EEN
EECS
SHFBUSY
EESK
EEDI
High
X
0
1
Z
Low
1
X
Active
1
Active
Low
0
1
From ECS
From EBUSY
From ESK Bit
From EEDI Bit
Bit of BCR19
of BCR19
Low
0
PVALID
LED1
LNKST