XE8000EV104 Semtech, XE8000EV104 Datasheet - Page 85

• Manufacturer Part Number: XE8000EV104
• Description: EVAL BOARD FOR XE8805AMI028LF
• Manufacturer: Semtech
• Type: MCUr

Specifications of XE8000EV104

• Contents: Fully Assembled Evaluation Board
• For Use With/related Products: XE88LC05AMI028
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Condition 2 is satisfied when S0=1 at the rising edge of S1. The bit UsrtCond2 in RegUsrtCond2 is set when the
condition 2 is detected and the USRT interface is enabled. Condition 2 is asserted for both modes (receiver and
transmitter). The UsrtCond2 bit is read only and is cleared by all reset conditions and by writing any data to its
address.
Condition 2 occurrence also generates an interrupt on Irq_cond2.
15.7 Interrupts or polling
In receive mode, there are two possibilities for detecting condition 1 or 2: the detection of the condition can
generate an interrupt or the registers can be polled (reading and checking the RegUsrtCond1 and RegUsrtCond2
registers for the status of USRT communication).
15.8 Function description
The bit UsrtEnable in RegUsrtCtrl is used to enable the USRT interface and controls the PB[4] and PB[5] pins.
This bit puts these two port B lines in the open drain configuration requested to use the USRT interface.
If no external pull-ups are added on PB[4] and PB[5], the user can activate internal pull-ups by setting PBPullup[4]
and PBPullup[5] in RegPBPullup.
The bits UsrtEnWaitS0, UsrtEnWaitCond1, UsrtWaitS0 in RegUsrtCtrl are used for transmitter/receiver control
of USRT interface.
Figure 15-3 shows the unconditional clock stretching function which is enabled by setting UsrtEnWaitS0.
When UsrtEnWaitS0 is 1, the S0 line will be maintained at 0 after its falling edge (clock stretching). UsrtWaitS0 is
then set to 1, indicating that the S0 line is forced low. One can release S0 by writing to the RegUsrtBufferS1
register.
The same can be done in combination with condition 1 detection by setting the UsrtEnWaitCond1 bit. Figure 15-4
shows the conditional clock stretching function which is enabled by setting UsrtEnWaitCond1.
© Semtech 2006
S0
UsrtWaitS0
write Reg UsrtBufferS1
Figure 15-3: S0 Stretching (UsrtEnWaitS0=1)
15-5
XE8805/05A
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