Datasheet

© 2011 Microchip Technology Inc. DS70116J-page 125
dsPIC30F5011/5013
18.6.2 20-BIT AC-LINK MODE
The 20-bit AC-Link mode allows all bits in the data time
slots to be transmitted and received but does not main-
tain data alignment in the TXBUF and RXBUF
registers.
The 20-bit AC-Link mode functions similar to the Multi-
Channel mode of the DCI module, except for the duty
cycle of the frame synchronization signal. The AC-Link
frame synchronization signal should remain high for 16
CSCK cycles and should be low for the following
240 cycles.
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 I
2
S Mode Operation
The DCI module is configured for I
2
S mode by writing
a value of ‘01’ to the COFSM<1:0> control bits in the
DCICON1 SFR. When operating in the I
2
S 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 I
2
S FRAME AND DATA WORD
LENGTH SELECTION
The WS and COFSG control bits are set to produce the
period for one half of an I
2
S 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 I
2
S frame.
18.7.2 I
2
S DATA JUSTIFICATION
As per the I
2
S specification, a data word transfer will, by
default, begin one CSCK cycle after a transition of the
WS signal. A ‘MSb left justified’ option can be selected
using the DJST control bit in the DCICON1 SFR.
If DJST = 1, the I
2
S 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.