ISLA214P50_1103 Datasheet, PDF (25/37 Pages) Intersil Corporation – 14-Bit, 500MSPS ADC Programmable Built-in Test Patterns

ISLA214P50
CSB
LAST LEGAL
CSB STALLING
SCLK
SDIO
INSTRUCTION/ADDRESS
DATA WORD 1
FIGURE 41. N-BYTE TRANSFER
DATA WORD N
Serial Peripheral Interface
A serial peripheral interface (SPI) bus is used to facilitate
configuration of the device and to optimize performance. The SPI
bus consists of chip select (CSB), serial clock (SCLK) serial data
output (SDO), and serial data input/output (SDIO). The maximum
SCLK rate is equal to the A/D sample rate (f_SAMPLE) divided by 32
for both write operations and read operations. At f_SAMPLE =
500MHz, maximum SCLK is 15.63MHz for writing and read
operations. There is no minimum SCLK rate.
The following sections describe various registers that are used to
configure the SPI or adjust performance or functional parameters.
Many registers in the available address space (0x00 to 0xFF) are
not defined in this document. Additionally, within a defined
register there may be certain bits or bit combinations that are
reserved. Undefined registers and undefined values within defined
registers are reserved and should not be selected. Setting any
reserved register or value may produce indeterminate results.
SPI Physical Interface
The serial clock pin (SCLK) provides synchronization for the data
transfer. By default, all data is presented on the serial data
input/output (SDIO) pin in three-wire mode. The state of the SDIO
pin is set automatically in the communication protocol
(described in the following). A dedicated serial data output pin
(SDO) can be activated by setting 0x00[7] high to allow operation
in four-wire mode.
The SPI port operates in a half duplex master/slave
configuration, with the ISLA214P50 functioning as a slave.
Multiple slave devices can interface to a single master in three-
wire mode only, since the SDO output of an unaddressed device
is asserted in four wire mode.
The chip-select bar (CSB) pin determines when a slave device is
being addressed. Multiple slave devices can be written to
concurrently, but only one slave device can be read from at a
given time (again, only in three-wire mode). If multiple slave
devices are selected for reading at the same time, the results will
be indeterminate.
The communication protocol begins with an instruction/address
phase. The first rising SCLK edge following a high to low
transition on CSB determines the beginning of the two-byte
instruction/address command; SCLK must be static low before
the CSB transition. Data can be presented in MSB-first order or
LSB-first order. The default is MSB-first, but this can be changed
by setting 0x00[6] high. Figures 36 and 37 show the appropriate
bit ordering for the MSB-first and LSB-first modes, respectively. In
MSB-first mode, the address is incremented for multi-byte
transfers, while in LSB-first mode it’s decremented.
In the default mode, the MSB is R/W, which determines if the
data is to be read (active high) or written. The next two bits, W1
and W0, determine the number of data bytes to be read or
written (see Table 4). The lower 13 bits contain the first address
for the data transfer. This relationship is illustrated in Figure 38,
and timing values are given in “Switching
Specifications Boldface limits apply over the operating
temperature range, -40°C to +85°C.” on page 13.
After the instruction/address bytes have been read, the
appropriate number of data bytes are written to or read from the
A/D (based on the R/W bit status). The data transfer will
continue as long as CSB remains low and SCLK is active. Stalling
of the CSB pin is allowed at any byte boundary
(instruction/address or data) if the number of bytes being
transferred is three or less. For transfers of four bytes or more,
CSB is allowed to stall in the middle of the instruction/address
bytes or before the first data byte. If CSB transitions to a high
state after that point the state machine will reset and terminate
the data transfer.
TABLE 4. BYTE TRANSFER SELECTION
[W1:W0]
BYTES TRANSFERRED
00
1
01
2
10
3
11
4 or more
Figures 40 and 41 illustrate the timing relationships for 2-byte
and N-byte transfers, respectively. The operation for a 3-byte
transfer can be inferred from these diagrams.
SPI Configuration
ADDRESS 0X00: CHIP_PORT_CONFIG
Bit ordering and SPI reset are controlled by this register. Bit order
can be selected as MSB to LSB (MSB first) or LSB to MSB (LSB
first) to accommodate various micro controllers.
Bit 7 SDO Active
Bit 6 LSB First
Setting this bit high configures the SPI to interpret serial data
as arriving in LSB to MSB order.
Bit 5 Soft Reset
Setting this bit high resets all SPI registers to default values.
Bit 4 Reserved
This bit should always be set high.
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FN7571.1
March 15, 2011