Harman Kardon AVR 245, Service Manual

Page: 191 / 228

M29W800DT, M29W800DB
10/42
SIGNAL DESCRIPTIONS
See Figure 2., Logic Diagram , and Table
1., Signal Names , for a brief overview of the sig-
nals connected to this device.
Address Inputs (A0-A18). The Address Inputs
select the cells in the memory array to access dur-
ing Bus Read operations. During Bus Write opera-
tions they control the commands sent to the
Command Interface of the internal state machine.
Data Inputs/Outputs (DQ0-DQ7). The Data In-
puts/Outputs output the data stored at the selected
address during a Bus Read operation. During Bus
Write operations they represent the commands
sent to the Command Interface of the internal state
machine.
Data Inputs/Outputs (DQ8-DQ14). The Data In-
puts/Outputs output the data stored at the selected
address during a Bus Read operation when BYTE
is High, V
IH
. When BYTE is Low, V
IL
, these pins
are not used and are high impedance. During Bus
Write operations the Command Register does not
use these bits. When reading the Status Register
these bits should be ignored.
Data Input/Output or Address Input (DQ15A-
1). When BYTE is High, V
IH
, this pin behaves as
a Data Input/Output pin (as DQ8-DQ14). When
BYTE is Low, V
IL
, this pin behaves as an address
pin; DQ15A–1 Low will select the LSB of the Word
on the other addresses, DQ15A–1 High will select
the MSB. Throughout the text consider references
to the Data Input/Output to include this pin when
BYTE is High and references to the Address In-
puts to include this pin when BYTE is Low except
when stated explicitly otherwise.
Chip Enable (E). The Chip Enable, E, activates
the memory, allowing Bus Read and Bus Write op-
erations to be performed. When Chip Enable is
High, V
IH
, all other pins are ignored.
Output Enable (G). The Output Enable, G, con-
trols the Bus Read operation of the memory.
Write Enable (W). The Write Enable, W, controls
the Bus Write operation of the memory’s Com-
mand Interface.
Reset/Block Temporary Unprotect (RP). The
Reset/Block Temporary Unprotect pin can be
used to apply a Hardware Reset to the memory or
to temporarily unprotect all Blocks that have been
protected.
A Hardware Reset is achieved by holding Reset/
Block Temporary Unprotect Low, V
IL
, for at least
t
PLPX
. After Reset/Block Temporary Unprotect
goes High, V
IH
, the memory will be ready for Bus
Read and Bus Write operations after t
PHEL
or
t
RHEL
, whichever occurs last. See the Ready/Busy
Output section, Table 15. and Figure 15., Reset/
Block Temporary Unprotect AC Waveforms , for
more details.
Holding RP at V
ID
will temporarily unprotect the
protected Blocks in the memory. Program and
Erase operations on all blocks will be possible.
The transition from V
IH
to V
ID
must be slower than
t
PHPHH
.
Ready/Busy Output (RB). The Ready/Busy pin
is an open-drain output that can be used to identify
when the device is performing a Program or Erase
operation. During Program or Erase operations
Ready/Busy is Low, V
OL
. Ready/Busy is high-im-
pedance during Read mode, Auto Select mode
and Erase Suspend mode.
After a Hardware Reset, Bus Read and Bus Write
operations cannot begin until Ready/Busy be-
comes high-impedance. See
Table 15., Reset/
Block Temporary Unprotect AC Characteristics
and Figure 15., Reset/Block Temporary Unprotect
AC Waveforms .
The use of an open-drain output allows the Ready/
Busy pins from several memories to be connected
to a single pull-up resistor. A Low will then indicate
that one, or more, of the memories is busy.
Byte/Word Organization Select (BYTE). The
Byte/Word Organization Select pin is used to
switch between the 8-bit and 16-bit Bus modes of
the memory. When Byte/Word Organization Se-
lect is Low, V
IL
, the memory is in 8-bit mode, when
it is High, V
IH
, the memory is in 16-bit mode.
V
CC
Supply Voltage. The V
CC
Supply Voltage
supplies the power for all operations (Read, Pro-
gram, Erase etc.).
The Command Interface is disabled when the V
CC
Supply Voltage is less than the Lockout Voltage,
V
LKO
. This prevents Bus Write operations from ac-
cidentally damaging the data during power up,
power down and power surges. If the Program/
Erase Controller is programming or erasing during
this time then the operation aborts and the memo-
ry contents being altered will be invalid.
A 0.1µF capacitor should be connected between
the V
CC
Supply Voltage pin and the V
SS
Ground
pin to decouple the current surges from the power
supply. The PCB track widths must be sufficient to
carry the currents required during program and
erase operations, I
CC3
.
V
SS
Ground. The V
SS
Ground is the reference for
all voltage measurements.
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AVR245
harman/kardon