XE8805 SEMTECH [Semtech Corporation], XE8805 Datasheet - Page 86

• Manufacturer Part Number: XE8805
• Description: Data Acquisition MCU
• Manufacturer: SEMTECH [Semtech Corporation]

When UsrtEnWaitCond1 is 1, the S0 signal will be stretched in its low state after its falling edge if the condition 1
has been detected before (UsrtCond1=1). UsrtWaitS0 is then set to 1, indicating that the S0 line is forced low.
One can release S0 by writing to the RegUsrtBufferS1 register.
Figure 15-5 shows the sampling function implemented by the UsrtBufferS1 bit. The bit UsrtBufferS1 in
RegUsrtBufferS1 is the value of S1 sampled on PB[4] at the last rising edge of S0. The bit UsrtEdgeS0 in
RegUsrtEdgeS0 is set to one on the same S0 rising edge and is cleared by a read operation of the
RegUsrtBufferS1 register. The bit therefore indicates that a new value is present in the RegUsrtBufferS1 which
has not yet been read.
© Semtech 2006
S1
S0
UsrtWaitS0
write Reg UsrtBufferS1
S1
S0
UsrtBufferS1
read Reg UsrtBufferS1
UsrtEdgeS0
Figure 15-4: Conditional stretching (UsrtEnWaitCond1=1)
Figure 15-5: S1 sampling
15-6
XE8805/05A
www.semtech.com