93C76/86
FIGURE 3-8:
CS
ERAL
STANDBY
CLK
...
DI
1
0
0
1
0
X
X
T
CZ
HIGH IMPEDANCE
DO
BUSY
READY
T
EC
ORG=V
CC
, 8 X’s
ORG=V
SS
, 9 X’s
Guarantee at V
CC
= +4.5V to +5.5V.
4.0
4.1
PIN DESCRIPTIONS
Chip Select (CS)
don't care inputs waiting for a new start condition to be
detected.
Note:
CS must go LOW between consecutive
instructions, except when performing a
sequential read (Refer to Section 3.1 for
more detail on sequential reads).
A HIGH level selects the device. A LOW level deselects
the device and forces it into standby mode. However, a
programming cycle which is already initiated will be
completed, regardless of the CS input signal. If CS is
brought LOW during a program cycle, the device will go
into standby mode as soon as the programming cycle
is completed.
CS must be LOW for 250 ns minimum (T
CSL
) between
consecutive instructions. If CS is LOW, the internal con-
trol logic is held in a RESET status.
4.3
Data In (DI)
Data In is used to clock in a START bit, opcode,
address, and data synchronously with the CLK input.
4.4
Data Out (DO)
4.2
Serial Clock (CLK)
The Serial Clock is used to synchronize the communi-
cation between a master device and the 93C76/86.
Opcode, address, and data bits are clocked in on the
positive edge of CLK. Data bits are also clocked out on
the positive edge of CLK.
CLK can be stopped anywhere in the transmission
sequence (at HIGH or LOW level) and can be continued
anytime with respect to clock HIGH time (T
CKH
) and
clock LOW time (T
CKL
). This gives the controlling mas-
ter freedom in preparing opcode, address, and data.
CLK is a “Don't Care” if CS is LOW (device deselected).
If CS is HIGH, but START condition has not been
detected, any number of clock cycles can be received
by the device without changing its status (i.e., waiting
for START condition).
CLK cycles are not required during the self-timed
WRITE (i.e., auto ERASE/WRITE) cycle.
After detection of a start condition the specified number
of clock cycles (respectively LOW to HIGH transitions of
CLK) must be provided. These clock cycles are
required to clock in all opcode, address, and data bits
before an instruction is executed (see Table 1-4 through
Data Out is used in the READ mode to output data syn-
chronously with the CLK input (T
PD
after the positive
edge of CLK).
This pin also provides READY/BUSY status information
during ERASE and WRITE cycles. READY/BUSY sta-
tus information is available when CS is high. It will be
displayed until the next start bit occurs as long as CS
stays high.
4.5
Organization (ORG)
When ORG is connected to V
CC
, the x16 memory orga-
nization is selected. When ORG is tied to V
SS
, the x8
memory organization is selected. There is an internal
pull-up resistor on the ORG pin that will select x16 orga-
nization when left unconnected.
4.6
Program Enable (PE)
This pin allows the user to enable or disable the ability
to write data to the memory array. If the PE pin is
floated or tied to V
CC
, the device can be programmed.
If the PE pin is tied to V
SS
, programming will be inhib-
ited. There is an internal pull-up on this device that
enables programming if this pin is left floating.
©
1996 Microchip Technology Inc.
Preliminary
DS21132C-page 9
MICROCHIP [ MICROCHIP TECHNOLOGY ]
