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SLAS052G – MARCH 1992 – REVISED JANUARY 2006
MODE 4: FAST MODE, CS ACTIVE (LOW) CONTINUOUSLY, 16-CLOCK TRANSFER
In this mode, CS is active (low) between serial I/O CLOCK transfers and each transfer must be exactly 16 clocks
long. After the initial conversion cycle, CS is held active (low) for subsequent conversions; the rising edge of
EOC then begins each sequence by removing DATA OUT from the low logic level, allowing the MSB of the
previous conversion to appear immediately on this output.
SLOW MODES
In a slow mode, the conversion is completed before the serial I/O CLOCK data transfer is completed. A slow
mode requires a minimum 11-clock transfer into I/O CLOCK, and the rising edge of the eleventh clock must
occur before the conversion period is complete; otherwise, the device loses synchronization with the host-serial
interface and CS has to be toggled to initialize the system. The eleventh rising edge of the I/O CLOCK must
occur within 9.5
µs
after the tenth I/O clock falling edge.
MODE 5: SLOW MODE, CS INACTIVE (HIGH) BETWEEN CONVERSION CYCLES, 11- to 16-CLOCK
TRANSFER
In this mode, CS is inactive (high) between serial I/O CLOCK transfers and each transfer can be 11 to 16 clocks
long. The falling edge of CS begins the sequence by removing DATA OUT from the high-impedance state. The
rising edge of CS ends the sequence by returning DATA OUT to the high-impedance state within the specified
delay time. Also, the rising edge of CS disables the I/O CLOCK and ADDRESS terminals within a setup time
plus two falling edges of the internal system clock.
MODE 6: SLOW MODE, CS ACTIVE (LOW) CONTINUOUSLY, 16-CLOCK TRANSFER
In this mode, CS is active (low) between serial I/O CLOCK transfers and each transfer must be exactly 16 clocks
long. After the initial conversion cycle, CS is held active (low) for subsequent conversions. The falling edge of
the sixteenth I/O CLOCK then begins each sequence by removing DATA OUT from the low state, allowing the
MSB of the previous conversion to appear immediately at DATA OUT. The device is then ready for the next
16-clock transfer initiated by the serial interface.
ADDRESS BITS
The 4-bit analog channel-select address for the next conversion cycle is presented to the ADDRESS terminal
(MSB first) and is clocked into the address register on the first four leading edges of I/O CLOCK. This address
selects one of 14 inputs (11 analog inputs or three internal test inputs).
ANALOG INPUTS AND TEST MODES
The 11 analog inputs and the three internal test inputs are selected by the 14-channel multiplexer according to
the input address as shown in Tables 2 and 3. The input multiplexer is a break-before-make type to reduce
input-to-input noise injection resulting from channel switching.
Sampling of the analog input starts on the falling edge of the fourth I/O CLOCK, and sampling continues for six
I/O CLOCK periods. The sample is held on the falling edge of the tenth I/O CLOCK. The three test inputs are
applied to the multiplexer, sampled, and converted in the same manner as the external analog inputs.
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