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PEB 20321
PEF 20321
Slave Register Descriptions
Data Sheet
228
2001-02-14
Tx Poll Register (TXPOLL)
Access
Offset Address
Reset Value
: read/write
: 2C
H
: 00000000
H
The Tx Poll Register provides an asserted low POLLn bit field per Serial PCM core
channel that allows host software to configure the MUNICH32X to respond in one of
three ways to a Tx idle condition, depending upon the state of the TXPOLL.POLLn bit
field (additionally, the states of the MODE2.SPOLL and MODE2.HPOLL bit fields are
evaluated in the Tx polling process).
The flow diagram in
Figure 76
illustrates the Tx polling process.
1. Most applications will set the Tx HOLD bit field in Tx descriptor and have both the
MODE2.SPOLL bit field and the MODE2.HPOLL bit field equal to zero. With this
configuration, the MUNICH32X will disable polling either immediately or after one poll
(depending upon the state of the TXPOLL.POLLn bit field). If TXPOLL.POLLn = 1, Tx
polling stops immediately, while if TXPOLL.POLLn = 0, a single poll is performed.
Software may enable a single poll for a particular channel by resetting the appropriate
TXPOLL.POLLn bit field. With this technique, bus utilization of idle channels is very
low, and startup from a temporary idle state is resumed after a simple write operation
to the MUNICH32X
’
s TXPOLL register.
2. If both the TXPOLL.POLLn bit field and the MODE2.SPOLL bit field are set, and the
MUNICH32X detects the Tx HOLD bit field set for that particular channel, then the
MUNICH32X will perform polling for all channels at a rate controlled by the Tx synch
pulses divided-by-8. Operation of this mode is described in detail in the SPOLL (slow
poll) section of the MODE2 Register.
3. If the TXPOLL.POLLn bit field is reset, while the MODE2.HPOLL bit field is set, and
the MUNICH32X detects the Tx HOLD bit field set for that particular channel, then the
MUNICH32X will perform Tx polling identical to that of the MUNICH32 (PEB 20320)
for that particular channel. In this case, the MUNICH32X checks the status of the
Tx HOLD bit field for each time slot assigned to this channel. In this way, if the bit has
been cleared, the MUNICH32X will immediately resume transmission. Although this
method is simpler (in concept) for the software design, it causes the MUNICH32X to
consume higher than normal bus bandwidth. For this reason, this is the least desirable
31
16
TXPOLL
POLL(31:16)
15
0
TXPOLL
POLL(15:0)