Lecture-8
Typical Memory Chips:
In previous lecture, the different types of static memories were
discussed. All these memories are random access memories. Any
memory location can be accessed in a random fashion without regard
to another location. The access time is same for each memory
locations. Memory chip may be volatile or non-volatile depending on
whether it is RWM or ROM. Some of the basic memory chips are
discussed below:
INTEL 2716 EPROM:
This is an Ultra Violet Erasable Programmable Read Only Memory
(UVEPROM). Intel 2716 has 16k bits (2k x 8= 16,384) or 2048 bytes
of memory. It has 11 address lines A10A9…..A1A0 and 8 data lines
D7…..D0. The pin connection & logic symbolism is shown in fig. (a)
and (b) respectively.
Figure (a) Figure (b)
Fig.2.19 Intel 2716 Read Only Memory
The pin details are given below:
Vcc, GND = +5V and Ground
A11-A0 = address lines
, D7-D0 = data lines
Vpp = Programming voltage pin
OE = output enable pin to enable the output data buffer.
CE/PROG= It is a dual function pin.
While programming Vpp pin must be held at 25 volts. It this chip is
used in a microcomputer after programming this pin must be held at
+5V.
This is an erasable PROM. The stored data can be erased by
exposing the window in the PROM to ultra violet light. Data may be
erased when continuously exposed in fluorescent light or sunlight.
When the EPROM is completely erased then each bit of the memory
must be ‘1’. If one wants to make it ‘0’, ’0’ should be written there.
Although, only 0s will be programmed, both 1s and 0s will be present
in the data word. Therefore, before programming each memory
location stores FFH and desired data can be stored by selectively
programming 0s into the designated bit locations. To store any data
at the addressed location a 50ms active programming pulse is
applied at PROG.
To program 2716, the following procedures are used;
i) Apply 25 V DC to pin no. 21(Vpp).
ii) Set the OE HIGH (+5V).
iii) Set up the address of the memory location to be programmed
at the address bus,
iv) Set up the 8-bit data to be programmed on the data bus,
v) Apply a 50 msec positive TTL pulse to the CE/PROG input.
Typical Memory Chips:
In previous lecture, the different types of static memories were
discussed. All these memories are random access memories. Any
memory location can be accessed in a random fashion without regard
to another location. The access time is same for each memory
locations. Memory chip may be volatile or non-volatile depending on
whether it is RWM or ROM. Some of the basic memory chips are
discussed below:
INTEL 2716 EPROM:
This is an Ultra Violet Erasable Programmable Read Only Memory
(UVEPROM). Intel 2716 has 16k bits (2k x 8= 16,384) or 2048 bytes
of memory. It has 11 address lines A10A9…..A1A0 and 8 data lines
D7…..D0. The pin connection & logic symbolism is shown in fig. (a)
and (b) respectively.
Figure (a) Figure (b)
Fig.2.19 Intel 2716 Read Only Memory
The pin details are given below:
Vcc, GND = +5V and Ground
A11-A0 = address lines
, D7-D0 = data lines
Vpp = Programming voltage pin
OE = output enable pin to enable the output data buffer.
CE/PROG= It is a dual function pin.
While programming Vpp pin must be held at 25 volts. It this chip is
used in a microcomputer after programming this pin must be held at
+5V.
This is an erasable PROM. The stored data can be erased by
exposing the window in the PROM to ultra violet light. Data may be
erased when continuously exposed in fluorescent light or sunlight.
When the EPROM is completely erased then each bit of the memory
must be ‘1’. If one wants to make it ‘0’, ’0’ should be written there.
Although, only 0s will be programmed, both 1s and 0s will be present
in the data word. Therefore, before programming each memory
location stores FFH and desired data can be stored by selectively
programming 0s into the designated bit locations. To store any data
at the addressed location a 50ms active programming pulse is
applied at PROG.
To program 2716, the following procedures are used;
i) Apply 25 V DC to pin no. 21(Vpp).
ii) Set the OE HIGH (+5V).
iii) Set up the address of the memory location to be programmed
at the address bus,
iv) Set up the 8-bit data to be programmed on the data bus,
v) Apply a 50 msec positive TTL pulse to the CE/PROG input.
