DSPIC30F MICROCHIP [Microchip Technology], DSPIC30F Datasheet - Page 144

• Manufacturer Part Number: DSPIC30F
• Description: General Purpose and Sensor Families High-Performance Digital Signal Controllers
• Manufacturer: MICROCHIP [Microchip Technology]

dsPIC30F
18.5
18.5.1
The DCI module has the ability to operate while in
Sleep mode and wake the CPU when the CSCK signal
is supplied by an external device (CSCKD = 1). The
DCI module will generate an asynchronous interrupt
when a DCI buffer transfer has completed and the CPU
is in Sleep mode.
18.5.2
If the DCISIDL control bit is cleared (default), the mod-
ule will continue to operate normally even in Idle mode.
If the DCISIDL bit is set, the module will halt when Idle
mode is asserted.
18.6
The AC-Link protocol is a 256-bit frame with one 16-bit
data slot, followed by twelve 20-bit data slots. The DCI
module has two Operating modes for the AC-Link pro-
tocol. These Operating modes are selected by the
COFSM<1:0> control bits in the DCICON1 SFR. The
first AC-Link mode is called ‘16-bit AC-Link mode’ and
is selected by setting COFSM<1:0> = 10. The second
AC-Link mode is called ‘20-bit AC-Link mode’ and is
selected by setting COFSM<1:0> = 11.
18.6.1
In the 16-bit AC-Link mode, data word lengths are
restricted to 16 bits. Note that this restriction only
affects the 20-bit data time slots of the AC-Link proto-
col. For received time slots, the incoming data is simply
truncated to 16 bits. For outgoing time slots, the 4 LS
bits of the data word are set to ‘0’ by the module. This
truncation of the time slots limits the A/D and DAC data
to 16 bits but permits proper data alignment in the
TXBUF and RXBUF registers. Each RXBUF and
TXBUF register will contain one data time slot value.
18.6.2
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.
DS70083G-page 142
DCI Module Operation During CPU
Sleep and Idle Modes
AC-Link Mode Operation
DCI MODULE OPERATION DURING
CPU SLEEP MODE
DCI MODULE OPERATION DURING
CPU IDLE MODE
16-BIT AC-LINK MODE
20-BIT AC-LINK MODE
Preliminary
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
The DCI module is configured for I
a value of ‘01’ to the COFSM<1:0> control bits in the
DCICON1 SFR. When operating in the I
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
The WS and COFSG control bits are set to produce the
period for one half of an I
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
18.7.2
As per the I
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 I
tified. The MS bit 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.
I
2
2
S Mode Operation
S frame.
2
I
LENGTH SELECTION
I
S specification, a data word transfer will, by
2
2
S FRAME AND DATA WORD
S DATA JUSTIFICATION
2
S data transfers will be MS bit left jus-
 2004 Microchip Technology Inc.
2
S data frame. That is, the
2
S mode by writing
2
S mode, the