LSI Logic Confidential
15-64
Serial I/O Port
Copyright © 2001, 2002 by LSI Logic Corporation. All rights reserved.
The length of a byte time is a function of the current
SIO_SPI_CLK frequency, the setting of inter-byte blank-
ing, and SIO_SPI_CS setup/hold (CSDL[2:0]).
SIO_SPI_MOSI is set to the value of the last bit sent by
the slave SPI device for each byte time. In bit-bang mode,
a minimum of two bytes are needed for one cycle of
SIO_SPI_CLK. Added to this is the time needed to hold
the bit stable for the entire byte time/interbyte blank,
SIO_SPI_CS[n] setup, and SIO_SPI_CS[n] hold. There-
fore, this mode is suitable only for low-frequency applica-
tions.
SPED
Clock Divider, LSB
30:24
The SIO_SPI_CLK frequency is determined by the follow-
ing equation:
SIO_SPI_CLK = sysclk / 2(p 2)
where progdiv = {HDIV, SPED}
(That is, progdiv is the concatenation of HDIV bits in the
SPI Clock Divider register with the SPED bits the SPI
Configuration register.)
HUEN
Host Update Enable
23
1 = Set the update mode to either single word mode or
host-polled mode. Values are given in
Table 15.8
SPI Transfer Modes
HUEN
ODW
ODR
Description
0
0
0
Single-word mode.
The SPI interface outputs BSIZ[1:0] + 1 bytes sourced from
SPI_TEMP and then completes the cycle. The BSIZ[1:0] + 1 bytes are
found in SPI_TEMP at the end of the cycle. The data in SPI_SHIFT
is undefined.
1
0
0
Host-polled mode.
All updates of BSIZ[1:0] + 1 bytes are done by the host. Access to the
SPI_TEMP register is indicated by the HAEN bit. After the current
word is transferred, the cycle stalls until the host writes the SPI_TEMP
register which clears the HAEN bit and allows the cycle to continue. If
the read data is needed, the host reads the SPI_TEMP register before
doing the write.
Содержание DMN-8600
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