TMS27C512 65536 BY 8-BIT UV ERASABLE
TMS27PC512 65536 BY 8-BIT
PROGRAMMABLE READ-ONLY MEMORIES
SMLS512G – NOVEMBER 1985 – REVISED SEPTEMBER 1997
initializing (TMS27PC512)
The one-time programmable TMS27PC512 PROM is provided with all bits in the logic high state, then logic lows
are programmed into the desired locations. Logic lows programmed into a PROM cannot be erased.
SNAP! Pulse programming
The 512K EPROM and OTP PROM are programmed using the TI SNAP! Pulse programming algorithm
illustrated by the flowchart in Figure 1, which programs in a nominal time of seven seconds. Actual programming
time varies as a function of the programmer used.
The SNAP! Pulse programming algorithm uses initial pulses of 100 microseconds (µs) followed by a byte
verification to determine when the addressed byte has been successfully programmed. Up to 10 (ten) 100-µs
pulses per byte are provided before a failure is recognized.
The programming mode is achieved with G / V
PP
= 13 V, V
CC
= 6.5 V, and E = V
IL
. Data is presented in parallel
(eight bits) on pins DQ0 to DQ7. Once addresses and data are stable, E is pulsed.
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
= 5 V, G / V
PP
= V
IL,
and E = V
IL
.
program inhibit
Programming can be inhibited by maintaining a high level input on the E pin.
program verify
Programmed bits can be verified when G/ V
PP
and E = V
IL
.
signature mode
The signature mode provides access to a binary code identifying the manufacturer and type. This mode is
activated when A9 is forced to 12 V. Two identifier bytes are accessed by toggling A0. All other addresses must
be held low. the signature code for these devices is 9785. A0 selects the manufacturer’s code 97 (Hex), and
A0 high selects the device code 85, as shown in Table 3.
Table 3. Signature Mode
IDENTIFIER†
Manufacturer Code
Device Code
PINS
A0
VIL
VIH
DQ7
1
1
DQ6
0
0
DQ5
0
0
DQ4
1
0
DQ3
0
0
DQ2
1
1
DQ1
1
0
DQ0
1
1
HEX
97
85
† E = G = VIL, A9 = VH, A1 – A8 = VIL, A10 – A15 = VIL, PGM = VIH or VIL.
4
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