Rainbow Electronics Preliminary - Manual (Page 3)

AT49F004/4096A(T)
3
AT49F004(T) Block Diagram
AT49F4096A(T) Block Diagram
Device Operation
READ: The AT49F004(T)/4096A(T) is accessed like an
EPROM. When CE and OE are low and WE is high, the
data stored at the memory location determined by the
address pins is asserted on the outputs. The outputs are
put in the high impedance state whenever CE or OE is
high. This dual-line control gives designers flexibility in pre-
venting bus contention.
COMMAND SEQUENCES: When the device is first pow-
ered on it will be reset to the read or standby mode
depending upon the state of the control line inputs. In order
to perform other device functions, a series of command
sequences are entered into the device. The command
sequences are shown in the Command Definitions table
(I/O8 - I/O15 are don’t care inputs for the command codes).
The command sequences are written by applying a low
pulse on the WE or CE input with CE or WE low (respec-
tively) and OE high. The address is latched on the falling
edge of CE or WE, whichever occurs last. The data is
latched by the first rising edge of CE or WE. Standard
microprocessor write timings are used. The address loca-
tions used in the command sequences are not affected by
entering the command sequences.
RESET: A RESET input pin is provided to ease some sys-
tem applications. When RESET is at a logic high level, the
VCC
GND
OE
CONTROL
LOGIC
DATA INPUTS/OUTPUTS
I/O0 - I/O7
DATA INPUTS/OUTPUTS
I/O0 - I/O7
WE
CE
RESET
ADDRESS
INPUTS
Y DECODER
INPUT/OUTPUT
BUFFERS
INPUT/OUTPUT
BUFFERS
PROGRAM DATA
LATCHES
PROGRAM DATA
LATCHES
Y-GATING
AT49F004 AT49F004T
Y-GATING
7FFFF 7FFFF
MAIN MEMORY
(480K BYTES)
BOOT BLOCK
16K BYTES
PARAMETER
BLOCK 2
8K BYTES
PARAMETER
BLOCK 1
8K BYTES
PARAMETER
BLOCK 1
8K BYTES
PARAMETER
BLOCK 2
8K BYTES
BOOT BLOCK
16K BYTES
MAIN MEMORY
480K BYTES
08000
07FFF
7C000
7BFFF
06000
05FFF
7A000
79FFF
X DECODER
04000
03FFF
78000
77FFF
00000 00000
VCC
GND
OE
CONTROL
LOGIC
DATA INPUTS/OUTPUTS
I/O0 - I/O15
DATA INPUTS/OUTPUTS
I/O0 - I/O15
WE
CE
RESET
ADDRESS
INPUTS
Y DECODER
INPUT/OUTPUT
BUFFERS
INPUT/OUTPUT
BUFFERS
PROGRAM DATA
LATCHES
PROGRAM DATA
LATCHES
Y-GATING
AT49F4096A AT49F4096AT
Y-GATING
3FFFF 3FFFF
MAIN MEMORY
(240K WORDS)
BOOT BLOCK
8K WORDS
PARAMETER
BLOCK 2
4K WORDS
PARAMETER
BLOCK 1
4K WORDS
PARAMETER
BLOCK 1
4K WORDS
PARAMETER
BLOCK 2
4K WORDS
BOOT BLOCK
8K WORDS
MAIN MEMORY
(240K WORDS)
04000
03FFF
3E000
3DFFF
03000
02FFF
3D000
3CFFF
X DECODER
02000
01FFF
3C000
3BFFF
00000 00000