WS57C45-25 STMICROELECTRONICS [STMicroelectronics], WS57C45-25 Datasheet - Page 5

• Manufacturer Part Number: WS57C45-25
• Description: HIGH-SPEED 2K x 8 REGISTERED CMOS PROM/RPROM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

WS57C45
FUNCTION DESCRIPTION
The WS57C45 is an electrically programmable read only memory produced with WSI’s patented high-performance
self-aligned split gate CMOS EPROM technology. It is organized as 2048 x 8 bits and is pin-for-pin compatible with
bipolar TTL fuse link PROMs. The WS57C45 includes a D-type 8-bit data register on-chip which reduces the
complexity and cost of microprogrammed pipelined systems where PROM data is held temporarily in a register. The
circuit features a programmable synchronous (OE
) or asynchronous (OE) output enable and asynchronous
S
initialization (INIT).
The programmed state of the enable pin (OE
or OE) will dictate the state of gthe outputs at power up. If OE
has
S
S
been programmed, the outputs will be in the OFF or high impedance state. If OE has been programmed, the
outputs will be OFF or high impedance only if the OE input is HIGH. Data is read by applying the address to inputs
A
– A
and a LOW to the enable input. The data is retrieved and loaded into the master section of the 8-bit data
10
0
register during the address set-up time. The data is transferred to the slave output of the data register at the next
LOW to HIGH clock (CP) transition. Then the output buffers present the data on the outputs (O
– O
).
7
0
When using the asynchronous enable (OE), the output buffers may be disabled at any time by switching the enable
input to a logic HIGH. They may be re-enabled by switching the enable to a logic LOW.
When using the sychronous enable (OE
), the outputs revert to a high impedance or OFF state at the next positive
S
clock edge following the OE
input transition to a HIGH state. The output will revert to the active state following a
S
positive clock edge when the OE
input is at a LOW state. The address and synchronous enable inputs are free to
S
change following a positive clock edge since the output will not change until the next low to high clock transition.
This enables accessing the next data location while previously addressed data is present on the outputs.
To avoid race conditions and simplify system timing, the 8-bit edge triggered data register clock is derived directly
from the system clock.
The WS57C45 has an asynchronous initialize input (INIT). This function can be used during power-up and time-out
periods to implement functions such as a start address or initialized bus control word. The INIT input enables the
contents of a 2049th 8-bit word to be loaded directly into the output data register. The INIT input can be used to
load any 8-bit data pattern into the register since each bit is programmable by the user. When unprogrammed,
activating INIT will result in clearing the register (outputs LOW). When all bits are programmed, actrivating INIT
results in PRESETting the register (outputs HIGH).
When activated LOW, the INIT input results in an immediate load of the 2049th word into both the master and slave
sections of the output register. This is independent of any other input including the clock (CP) input. The initialize
data will be present at the outputs after the asynchronous enable (OE) is taken to a LOW state.
Programming Information
Apply power to the WS57C45 for normal read mode operation with CP/PGM, OE/OE
and INIT/V
at V
. Then
S
PP
IH
take INIT/V
to V
. The part is then in the program inhibit mode operation and the output lines are in a high
PP
PP
impedance state. Refer to Figure 5. As shown in Figure 5, address, program and verify one byte of data. Repeat
this sequence for each location to be programmed.
When intelligent programming is used, the program pulse width is 1 ms in length. Each address location is
programmed and verified until it verifies correctly up to and including 5 times. After the location verifies, an
additional programming pulse should be applied that is X1 times in duration of the sum of the previous programming
pulses before proceeding on to the next address and repeating the process.
Initialization Byte Programming
The WS57C45 has a 2049th byte of data that can be used to initialize the value of the data register. This byte
contains the value “0” when it is shipped from the factory. The user must program the 2049th byte with a value other
than “0” for data register initialization if that value is not desired. Except for the following details, the user may
program the 2049th byte in the same manner as the other 2048 bytes. First, since all 2048 addresses are used up,
a super voltage address feature is used to enable an additional address. The actual address includes V
on A
PP
1
and V
on A
. Refer to the Mode Selection table. The programming and verification of the Initial Byte is
IL
2
accomplished operationally by performing an initialize function.
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