
Data Sheet
June 2001
DSP16410B Digital Signal Processor
158
Agere Systems—Proprietary
Use pursuant to Company instructions
Agere Systems Inc.
4 Hardware Architecture
(continued)
4.16 Serial Interface Unit (SIU)
(continued)
4.16.4 Basic Output Processing
(continued)
The DMAU or either of the cores writes output data into
SODR
(serial output data register). See
Figure 40 on
page 152
. If
SODR
is empty, the SIU clears the SODV
flag (serial output data valid,
STAT
[3]—
Table 116 on
page 194
). This indicates that a core or the DMAU can
write new data to
SODR
. The following describes the
sequence of events that follow this condition:
1. The SIU signals the DMAU that it is ready to accept
new data. If the OINTSEL[1:0] field
(
SCON10
[14:13]) equals two, the SIU generates the
SOINT interrupt signal to both cores.
2. The DMAU or one of the cores writes
SODR
with
new data.
3. The SIU sets SODV to indicate that
SODR
is full.
4. At the beginning of the time slot for the next active
channel (on an activating edge of the output bit
clock), the SIU transfers the contents of
SODR
to the
16-bit output shift register, clears SODV, and drives
the first data bit onto SOD. While transferring the
data from
SODR
to the output shift register, the SIU
formats the data (μ-law, A-law, or no modification)
according to the value of the OFORMAT[1:0] field
(
SCON0
[9:8]—see
Table 101 on page 182
). Based
on the value of the OMSB field (
SCON0
[10]), the
SIU shifts the data out LSB-first or MSB-first. Based
on the value of the OSIZE[1:0] field (
SCON0
[12:11]),
the SIU drives 4, 8, 12, or 16 bits of the data in the
output shift register onto SOD. If OSIZE[1:0] is pro-
grammed to select a data size of 4, 8, or 12 bits, the
data must be right-justified (placed in the least signif-
icant bits) of the 16-bit
SODR
register.
Output buffer underflow can occur if the DMAU or core
does not write new data into
SODR
before the contents
of
SODR
is to be transferred to the output shift register.
Specifically, an output buffer underflow occurs if all
three of the following conditions exist:
SODR
is empty (SODV = 0).
The output shift register is empty.
The time slot for an active channel is pending.
If output buffer underflow occurs, the SIU sets the
OUFLOW field (
STAT
[7]) and continues to output the
old data in
SODR
(repeats step 4) for any active chan-
nels until the DMAU or core writes new data to
SODR
.
If the OINTSEL[1:0] field (
SCON10
[14:13]) equals
three, the SIU asserts the SOINT interrupt to notify the
cores of the underflow condition.
4.16.5 Clock and Frame Sync Generation
Generation of the SIU bit clocks (SICK and SOCK) and
frame syncs (SIFS and SOFS) can be active or pas-
sive. In active mode, these signals can be derived
from the DSP clock, CLK, or from an external clock
source applied to the SCK pin. In either case, the
active clock source is divided down by a programmable
clock divider to generate the desired bit clock and
frame sync frequencies. In passive mode, the external
clock source applied to the SICK pin is used directly as
the input bit clock, the signal applied to SIFS is used
directly as the input frame sync, the clock source
applied to the SOCK pin is used directly as the output
bit clock, and the signal applied to SOFS is used as the
output frame sync. All of the bit fields that control bit
clock and frame sync generation are summarized in
Table 90 on page 161
.
The input section and the output section of each SIU
operate independently and require individual clock
sources to be specified.
Note:
The combination of passive input bit clock and
active input frame sync is not supported, and the
combination of passive output bit clock and
active output frame sync is not supported. If the
combination of an active bit clock and a passive
frame sync is selected, the frame sync must be
derived from the bit clock and must meet the tim-
ing requirements specified in
Section 11.11
.
The default operation specifies that the SIU clocks
input data bits from SID on the falling edge of SICK and
drive output data bits onto SOD on the rising edge of
SOCK. The DSP16410B can invert the polarity (active
level) of the SICK pin by setting the ICKK field
(
SCON10
[3]—see
Table 111 on page 188
) and the
polarity (active level) of the SOCK pin by setting the
OCKK field (
SCON10
[7]). The SIU can generate one
or both bit clocks internally (active) or externally
(passive). Setting the ICKA field (
SCON10
[2]) puts
SICK into active mode, and setting the OCKA field
(
SCON10
[6]) puts SOCK into active mode.