參數(shù)資料
型號: ENC624J600T-I/PT
廠商: Microchip Technology
文件頁數(shù): 69/168頁
文件大小: 0K
描述: IC ETHERNET CTRLR W/SPI 64-TQFP
視頻文件: Fast 100 Mbps Ethernet PICtail Plus Overview
標(biāo)準(zhǔn)包裝: 1,200
控制器類型: 以太網(wǎng)控制器(IEEE 802.3)
接口: SPI
電源電壓: 3 V ~ 3.6 V
電流 - 電源: 96mA
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 64-TQFP
供應(yīng)商設(shè)備封裝: 64-TQFP(10x10)
包裝: 帶卷 (TR)
配用: AC164132-ND - BOARD DAUGHTER PICTAIL ETHERNET
PIC18F2220/2320/4220/4320
DS39599G-page 158
2007 Microchip Technology Inc.
17.3.2
OPERATION
When initializing the SPI, several options need to be
specified. This is done by programming the appropriate
control bits (SSPCON1<5:0> and SSPSTAT<7:6>).
These control bits allow the following to be specified:
Master mode (SCK is the clock output)
Slave mode (SCK is the clock input)
Clock Polarity (Idle state of SCK)
Data Input Sample Phase (middle or end of data
output time)
Clock Edge (output data on rising/falling edge of
SCK)
Clock Rate (Master mode only)
Slave Select mode (Slave mode only)
The MSSP consists of a Transmit/Receive Shift regis-
ter (SSPSR) and a Buffer register (SSPBUF). The
SSPSR shifts the data in and out of the device, MSb
first. The SSPBUF holds the data that was written to the
SSPSR until the received data is ready. Once the 8 bits
of data have been received, that byte is moved to the
SSPBUF register. Then the Buffer Full Detect bit, BF
(SSPSTAT<0>), and the interrupt flag bit, SSPIF, are
set. This double-buffering of the received data
(SSPBUF) allows the next byte to start reception before
reading the data that was just received. Any write to the
SSPBUF register during transmission/reception of data
will be ignored and the Write Collision Detect bit,
WCOL (SSPCON1<7>), will be set. User software
must clear the WCOL bit so that it can be determined if
the following write(s) to the SSPBUF register
completed successfully.
When the application software is expecting to receive
valid data, the SSPBUF should be read before the next
byte of data to transfer is written to the SSPBUF. Buffer
Full bit, BF (SSPSTAT<0>), indicates when SSPBUF
has been loaded with the received data (transmission
is complete). When the SSPBUF is read, the BF bit is
cleared. This data may be irrelevant if the SPI is only a
transmitter. Generally, the MSSP interrupt is used to
determine when the transmission/reception has com-
pleted. The SSPBUF must be read and/or written. If the
interrupt method is not going to be used, then software
polling can be done to ensure that a write collision does
not occur. Example 17-1 shows the loading of the
SSPBUF (SSPSR) for data transmission.
The SSPSR is not directly readable or writable and can
only be accessed by addressing the SSPBUF register.
Additionally, the MSSP Status register (SSPSTAT)
indicates the various status conditions.
EXAMPLE 17-1:
LOADING THE SSPBUF (SSPSR) REGISTER
LOOP
BTFSS
SSPSTAT, BF
;Has data been received(transmit complete)?
BRA
LOOP
;No
MOVF
SSPBUF, W
;WREG reg = contents of SSPBUF
MOVWF
RXDATA
;Save in user RAM, if data is meaningful
MOVF
TXDATA, W
;W reg = contents of TXDATA
MOVWF
SSPBUF
;New data to xmit
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