Data Sheet
June 2001
DSP16410B Digital Signal Processor
174
Agere Systems—Proprietary
Use pursuant to Company instructions
Agere Systems Inc.
4 Hardware Architecture
(continued)
4.16 Serial Interface Unit (SIU)
(continued)
4.16.13 Channel Mode—Up to 128 Channels in a
Maximum of Eight Subframes
The SIU has the ability to process a maximum of 128
channels in channel mode if the SIU control is properly
synchronized with core intervention. The steps
required for the additional channel processing are the
same as for the channel mode discussed in
Section 4.16.12
. However, the SIU control registers
must be reconfigured with greater frequency, costing
additional core overhead. In this case, subframe acti-
vation and channel definition within a subframe can
occur as often as every subframe boundary.
The SIU has the ability to interrupt either core at frame
boundaries, subframe boundaries, channel bound-
aries, or if an error is detected (overflow or underflow).
The interrupt signal trigger is determined by the IINT-
SEL[1:0] field (
SCON10
[12:11]—see
Table 111 on
page 188
) for input processing and by the OINT-
SEL[1:0] field (
SCON10
[14:13]) for output processing.
When servicing subframe boundary interrupts gener-
ated by SIU0 or SIU1, either CORE0 or CORE1 can
modify the input and output subframe and channel con-
trol fields without affecting the current subframe being
processed. Specifically, the cores can modify the
OSFID_E[1:0] and OSFID_O[1:0] fields (
SCON3
—see
Table 104 on page 185
), the ISFID_E[1:0] and
ISFID_O[1:0] fields (
SCON3
—see
Table 104 on
page 185
), the ISFVEC_E[15:0] field (
SCON4
—see
Table 105 on page 186
), the ISFVEC_O[15:0] field
(
SCON5
—see
Table 106 on page 186
), the
OSFVEC_E[15:0] field (
SCON6
—see
Table 107 on
page 187
), the OSFVEC_O[15:0] field (
SCON7
—see
Table 108 on page 187
), the OSFMSK_E[15:0] field
(
SCON8
—see
Table 109 on page 187
), and the
OSFMSK_O[15:0] field (
SCON9
—see
Table 110 on
page 187
). This is also true for the
ICIX0
,
ICIX1
,
OCIX0
, and
OCIX1
registers (see
Table 120 on
page 196
and
Table 119 on page 195
). The SIU
latches the values in these control bit fields at the
beginning of every subframe.
If one of the cores uses this feature in an SIINT or
SOINT interrupt service routine (ISR), the SIU can be
programmed to individually select channels for input or
output anywhere within the frame. The user can take
advantage of this feature by updating the input and out-
put subframe and channel control fields after each sub-
frame is processed, allowing channels in more than two
subframes to be processed during each frame. This
requires the ISR to count the subframe interrupts and
program the necessary SIU control registers with the
appropriate values to process the next desired sub-
frame. The user also has the option of programming
the input and output subframe and channel control
fields two subframes in advance, as these bit fields are
double-buffered. For example, if the active subframe is
even, the user’s ISR can reprogram the control bit fields
with the appropriate values for the next even subframe
without disturbing the processing of the currently active
subframe.
In channel mode, the SIU drives data onto the SOD pin
only during the time slots for active output channels.
Otherwise, the SIU 3-states SOD. Similarly, in channel
mode, the SIU latches input data bits only during the
time slots for active input channels.