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參數(shù)資料
| 型號(hào)： | TMS27C040-15 |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | Programmable Read-Only Memory(512K×8結(jié)構(gòu),可擦可編程只讀存儲(chǔ)器) |
| 中文描述： | 可編程只讀存儲(chǔ)器（為512k × 8結(jié)構(gòu)，可擦可編程只讀存儲(chǔ)器） |
| 文件頁數(shù)： | 3/11頁 |
| 文件大小： | 236K |
| 代理商： | TMS27C040-15 |
TMS27C040 4194304-BIT UV ERASABLE PROGRAMMABLE
TMS27PC040 4194304-BIT PROGRAMMABLE
READ-ONLY MEMORY
SMLS040E – NOVEMBER 1990 – REVISED JUNE 1995
3
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
power down
Active I
CC
supply current can be reduced from 50 mA to 1 mA 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 (TMS27C040)
Before programming, the TMS27C040 EPROM 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 TMS27C040, 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.
initializing (TMS27PC040)
The one-time programmable TMS27PC040 PROM is provided with all bits in logic high state, then logic lows
are programmed into the desired locations. Logic lows programmed into an OTP PROM cannot be erased.
SNAP! Pulse programming
The TMS27C040 and TMS27PC040 are programmed by using the SNAP! Pulse programming algorithm. The
programming sequence is shown in the SNAP! Pulse programming flow chart (Figure 1).
The initial setup is V
PP
= 13 V, V
CC
= 6.5 V, E = V
IH
, and G = V
IH
. Once the initial location is selected, the data
is presented in parallel (eight bits) on pins DQ0 through DQ7. Once addresses and data are stable, the
programming mode is achieved when E is pulsed low (V
IL
) with a pulse duration of t
w(PGM)
. Every location is
programmed only once before going to interactive mode.
In the interactive mode, the word is verified at V
PP
= 13 V, V
CC
= 6.5 V, E = V
IH
, and G = V
IL
. If the correct data
is not read, the programming is performed by pulling E low with a pulse duration of t
w(PGM)
. This sequence of
verification and programming is performed up to a maximum of 10 times. When the device is fully programmed,
all bytes are verified with V
CC
= V
PP
= 5 V
±
10%.
program inhibit
Programming can be inhibited by maintaining high level inputs on the E and G pins.
program verify
Programmed bits can be verified with V
PP
= 13 V when G = V
IL
, and E = 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 TMS27C040 is 9750. A0 low selects the manufacturer’s
code 97 (Hex), and A0 high selects the device code 50 (Hex), as shown by the signature mode table below.
IDENTIFIER
PINS
A0
VIL
VIH
DQ7
1
DQ6
0
DQ5
0
DQ4
1
DQ3
0
DQ2
1
DQ1
1
DQ0
1
HEX
97
MANUFACTURER CODE
DEVICE CODE
0
1
0
1
0
0
0
0
50
E = G = VIL, A1-A8 = VIL, A9 = VH, A10-A18 = VIL, VPP = VCC.
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