NS7520B-1-I46 Digi International, NS7520B-1-I46 Datasheet - Page 224

• Manufacturer Part Number: NS7520B-1-I46
• Description: IC ARM MICROPROCESSOR 177BGA
• Manufacturer: Digi International
• Series: NET+ARM®r

Specifications of NS7520B-1-I46

• Applications: Network Processor
• Core Processor: ARM7
• Program Memory Type: External Program Memory
• Controller Series: -
• Ram Size: External
• Interface: EBI/EMI, Ethernet, DMA, SPI, UART
• Number Of I /o: 16
• Voltage - Supply: 1.4 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 177-LFBGA
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

FIFO management
2 1 2
S P I m o d e
Note:
Data flow between the SPI master/slave interfaces and memory occurs through the
FIFO blocks within the SER module. Each serial port provides a 32-byte transmit FIFO
and a 32-byte receive FIFO. Both the transmit and receive FIFOs are memory-mapped
to the processor address space.
Transmit FIFO interface
The processor can write either 1, 2, or 4 bytes at a time to the transmit FIFO. The
number of bytes written is controlled by the data size defined by the ARM processor
as shown in these examples:
Operating in Endian modes
C
C
C
Assembler
Assembler
Assembler
Terminology
Information transfer is also qualified with an enable signal. The SPI enable
signal must be active low for data transfer to occur, regardless of the SPI
clock signal. The SPI enable function allows multiple slaves to be
individually addressed in a multi-drop configuration.
Big Endian mode configuration. Transmits first the most significant bytes in
the word written to the FIFO. For example, the long word
in the character
Little Endian mode configuration. Transmits first the least significant bytes
in the word written to the FIFO. For example, the long word
N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v G 9 / 2 0 0 7
The NS7520 supports only SPI modes 0 and 1. See Figure 25, "SPI master
mode 0 and 1 two-byte transfer," on page 217 and Figure 26, "SPI slave
mode 0 and 1 two-byte transfer," on page 220 for illustrations.
Byte using a byte pointer
2 bytes using a short pointer
4 bytes using a standard long word pointer
Byte
Half word
Long word
What’s being written
0x11
being transmitted first and
(char*)0xffd00010=(char)data
(short)0xffd00010=(short)data
(long)0xffd00010=(long)data
STRB instructions
STRH instructions
STR instructions
Value
0x44
being transmitted last.
0x11223344
0x11223344
results