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McASP Registers
Table 22-44. Transmitter Status Register (XSTAT) Field Descriptions (continued)
Bit Field Value Description
1 XSYNCERR Unexpected transmit frame sync flag. XSYNCERR is set when a new transmit frame sync (AFSX)
occurs before it is expected. Causes a transmit interrupt (XINT), if this bit is set and XSYNCERR in
XINTCTL is set. This bit is cleared by writing a 1 to this bit. Writing a 0 has no effect.
0 Unexpected transmit frame sync did not occur.
1 Unexpected transmit frame sync did occur.
0 XUNDRN Transmitter underrun flag. XUNDRN is set when the transmit serializer is instructed to transfer data
from XBUF to XRSR, but XBUF has not yet been serviced with new data since the last transfer. Causes
a transmit interrupt (XINT), if this bit is set and XUNDRN in XINTCTL is set. This bit is cleared by writing
a 1 to this bit. Writing a 0 has no effect.
0 Transmitter underrun did not occur.
1 Transmitter underrun did occur. For details on McASP action upon underrun conditions, see Buffer
Underrun Error - Transmitter.
22.4.1.34 Current Transmit TDM Time Slot Register (XSLOT)
The current transmit TDM time slot register (XSLOT) indicates the current time slot for the transmit data
frame. The XSLOT is shown in Figure 22-72 and described in Table 22-45.
Figure 22-72. Current Transmit TDM Time Slot Register (XSLOT)
31 16
Reserved
R-0
15 10 9 0
Reserved XSLOTCNT
R-0 R-17Fh
LEGEND: R = Read only; -n = value after reset
Table 22-45. Current Transmit TDM Time Slot Register (XSLOT) Field Descriptions
Bit Field Value Description
31-10 Reserved 0 Reserved. The reserved bit location always returns the default value. A value written to this field has no
effect. If writing to this field, always write the default value for future device compatibility.
9-0 XSLOTCNT 0-17Fh Current transmit time slot count. Legal values: 0 to 383 (17Fh).
During reset, this counter value is 383 so the next count value, which is used to encode the first DIT
group of data, will be 0 and encodes the B preamble.
TDM function is not supported for >32 time slots. However, TDM time slot counter may count to 383
when used to transmit a DIT block.
3871
SPRUH73H–October 2011–Revised April 2013 Multichannel Audio Serial Port (McASP)
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