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| 型號： | TMS27C020-20FML |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | READ-ONLY MEMORIES |
| 中文描述： | 只讀存儲器 |
| 文件頁數(shù)： | 3/15頁 |
| 文件大?。?/td> | 206K |
| 代理商： | TMS27C020-20FML |
TMS27C020 262144 BY 8-BIT UV ERASABLE
TMS27PC020 262144 BY 8-BIT
PROGRAMMABLE READ-ONLY MEMORIES
SMLS020C – NOVEMBER 1990 – REVISED SEPTEMBER 1997
3
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
read/output disable
When the outputs of two or more TMS27C020s or TMS27PC020s are connected in parallel on the same bus,
the output of any particular device in the circuit can be read with no interference from competing outputs of the
other devices. To read the output of a single device, a low level signal is applied to the E and G pins. All other
devices in the circuit should have their outputs disabled by applying a high level signal to one of these pins.
latchup immunity
Latchup immunity on the TMS27C020 and TMS72PC020 is a minimum of 250 mA on all inputs and outputs.
This feature provides latchup immunity beyond any potential transients at the P.C. board level when the EPROM
is interfaced to industry standard TTL or MOS logic devices. The input/output layout approach controls latchup
without compromising performance or packing density.
power down
Active I
CC
supply current can be reduced from 30 mA to 500
μ
A by applying a high TTL input on E and to
100
μ
A by applying a high CMOS input on E. In this mode all outputs are in the high-impedance state.
erasure
Before programming, the TMS27C020 is erased by exposing the chip through the transparent lid to a high
intensity ultraviolet light (wavelength 2537 ). The recommended minimum exposure dose
(UV intensity
×
exposure time) is 15-W
s/cm
2
. A typical 12-mW/cm
2
, filterless UV lamp erases the device in
21 minutes. The lamp should be located about 2.5 cm above the chip during erasure. After erasure, all bits are
in the high state. It should be noted that normal ambient light contains the correct wavelength for erasure.
Therefore, when using the TMS27C020, the window should be covered with an opaque label. After erasure (all
bits in logic high state), logic lows are programmed into the desired locations. A programmed low can be erased
only by ultraviolet light.
SNAP! Pulse programming
The TMS27C020 and TMS27PC020 are programmed using the TI SNAP! Pulse programming algorithm,
illustrated by the flowchart in Figure 1, which programs in a nominal time of twenty-six seconds. Actual
programming time varies as a function of the programmer used.
The SNAP! Pulse programming algorithm uses an initial pulse of 100 microseconds (
μ
s) followed by a byte
verification to determine when the addressed byte has been successfully programmed. Up to ten 100-
μ
s pulses
per byte are provided before a failure is recognized.
The programming mode is achieved when V
PP
equals 13 V, V
CC
= 6.5 V, E = V
IL
, G = V
IH
. Data is presented
in parallel (eight bits) on pins DQ0 through DQ7. Once addresses and data are stable, PGM is pulsed low.
More than one device can be programmed when the devices are connected in parallel. Locations can be
programmed in any order. When the SNAP! Pulse programming routine is complete, all bits are verified with
V
CC
= V
PP
= 5 V
±
10%.
program inhibit
Programming can be inhibited by maintaining a high level input on the E or PGM pins.
program verify
Programmed bits can be verified with V
PP
equals 13 V when G = V
IL
, E = V
IL
, and PGM = V
IH
.
signature mode
The signature mode provides access to a binary code identifying the manufacturer and type. This mode is
activated when A9 (pin 26) is forced to 12 V. Two identifier bytes are accessed by toggling A0. All other
addresses must be held low. The signature code for the TMS27C020 is 9732. A0 low selects the manufacturer’s
code 97 (Hex), and A0 high selects the device code 32 (Hex), as shown in Table 3.
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| TMS27C020-20JE | READ-ONLY MEMORIES |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TMS27C020-20JE | 制造商:TI 制造商全稱:Texas Instruments 功能描述:READ-ONLY MEMORIES |
| TMS27C020-20JE4 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:x8 EPROM |
| TMS27C020-20JL | 制造商:TI 制造商全稱:Texas Instruments 功能描述:READ-ONLY MEMORIES |
| TMS27C020-20JL4 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:x8 EPROM |
| TMS27C020-25 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:READ-ONLY MEMORIES |
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