HI1-574ATD/883 INTERSIL [Intersil Corporation], HI1-574ATD/883 Datasheet - Page 12

• Manufacturer Part Number: HI1-574ATD/883
• Description: Complete, 12-Bit A/D Converters with Microprocessor Interface
• Manufacturer: INTERSIL [Intersil Corporation]

that a particular input controls the start of conversion, the
other two should be set up at least 50ns earlier. See the
HI-X74A Timing Specifications, Convert Mode.
This variety of HI-X74A control modes allows a simple
interface in most system applications. The Convert Start
timing relationships are illustrated in Figure 4.
The output signal STS indicates status of the converter by
going high only while a conversion is in progress. While STS
is high, the output buffers remain in a high impedance state
and data cannot be read. Also, an additional Start Convert
will not reset the converter or reinitiate a conversion while
STS is high.
Reading the Output Data
The output data buffers remain in a high impedance state
until four conditions are met: R/C high, STS low, CE high and
CS low. At that time, data lines become active according to
the state of inputs 12/8 and A
illustrated in Figure 5.
The 12/8 input will be tied high or low in most applications,
though it is fully TTL/CMOS-compatible. With 12/8 high, all
12 output lines become active simultaneously, for interface to
a 12-bit or 16-bit data bus. The A
DB11-DB0
See HI-X74A Timing Specifications for more information.
STS
R/C
CE
CS
A
O
t
t
SSC
t
SRC
FIGURE 3. CONVERT START TIMING
SAC
t
HRC
t
HAC
t
DSC
HIGH IMPEDANCE
12
O
. Timing constraints are
O
t
t
HEC
HSC
input is ignored.
t
C
With 12/8 low, the output is organized in two 8-bit bytes,
selected one at a time by A
to be connected as shown in Figure 6. A
the least significant bit of the address bus, for storing the
HI-X74A output in two consecutive memory locations. (With
A
are disabled, bits 4 through 7 are forced low, and the 4 LSBs
are enabled). This two byte format is considered “left justified
data,” for which a decimal (or binary!) point is assumed to the
left of byte 1:
Further, A
the converter. Break-before-make action is guaranteed
between the two data bytes, which assures that the outputs
strapped together in Figure 6 will never be enabled at the
same time.
A read operation usually begins after the conversion is
complete and STS is low. For earliest access to the data,
however, the read should begin no later than (t
before STS goes low. See Figure 5.
DB11-DB0
MSB
O
X
low, the 8 MSBs only are enabled. With A
See HI-X74A Timing Specifications for more information.
STS
R/C
X
CE
CS
A
O
X
O
may be toggled at any time without damage to
BYTE 1
X
FIGURE 4. READ CYCLE TIMING
X
X
X
HIGH IMPEDANCE
O
X
t
t
t
. This allows an 8-bit data bus
SRR
SAR
SSR
t
DD
t
HS
X
X
t
t
t
HSR
HRR
HAR
X
O
LSB
is usually tied to
BYTE 2
VALID
X
DATA
O
high, 4 MSBs
DD
0
+ t
0
t
HL
t
HS
HD
0
)
0