
2006 Microchip Technology Inc.
DS70117F-page 133
dsPIC30F6011/6012/6013/6014
The 20-bit mode treats each 256-bit AC-Link frame as
sixteen, 16-bit time slots. In the 20-bit AC-Link mode,
the module operates as if COFSG<3:0> = 1111 and
WS<3:0> = 1111. The data alignment for 20-bit data
slots is ignored. For example, an entire AC-Link data
frame can be transmitted and received in a packed
fashion by setting all bits in the TSCON and RSCON
SFRs. Since the total available buffer length is 64 bits,
it would take 4 consecutive interrupts to transfer the
AC-Link frame. The application software must keep
track of the current AC-Link frame segment.
18.7
I2S Mode Operation
The DCI module is configured for I2S mode by writing
a value of ‘01’ to the COFSM<1:0> control bits in the
DCICON1 SFR. When operating in the I2S mode, the
DCI module will generate frame synchronization sig-
nals with a 50% duty cycle. Each edge of the frame
synchronization signal marks the boundary of a new
data word transfer.
The user must also select the frame length and data
word size using the COFSG and WS control bits in the
DCICON2 SFR.
18.7.1
I2S FRAME AND DATA WORD
LENGTH SELECTION
The WS and COFSG control bits are set to produce the
period for one half of an I2S data frame. That is, the
frame length is the total number of CSCK cycles
required for a left or a right data word transfer.
The BLEN bits must be set for the desired buffer length.
Setting BLEN<1:0> = 01 will produce a CPU interrupt,
once per I2S frame.
18.7.2
I2S DATA JUSTIFICATION
As per the I2S specification, a data word transfer will, by
default, begin one CSCK cycle after a transition of the
WS signal. A ‘MS bit left justified’ option can be
selected using the DJST control bit in the DCICON2
SFR.
If DJST = 1, the I2S data transfers will be MSb left jus-
tified. The MSb of the data word will be presented on
the CSDO pin during the same CSCK cycle as the ris-
ing or falling edge of the COFS signal. The CSDO pin
is tri-stated after the data word has been sent.