Datasheet

459
32133D–11/2011
UC3D
23.9.3 SMBus Timing Register
Name:
SMBTR
Access Type: Read/Write
Offset: 0x08
Reset Value: 0x00000000
• EXP: SMBus Timeout Clock Prescaler
Used to specify how to prescale the TIM and TLOWM counters in SMBTR. Counters are prescaled according to the following
formula
• THMAX: Clock High Maximum Cycles
Clock cycles in clock high maximum count. Prescaled by SMBTR.EXP. Used for bus free detection. Used to time T
HIGH:MAX
.
NOTE: Uses the prescaler specified by CWGR, NOT the prescaler specified by SMBTR.
• TLOWM: Master Clock Stretch Maximum Cycles
Clock cycles in master maximum clock stretch count. Prescaled by SMBTR.EXP. Used to time T
LOW:MEXT
• TLOWS: Slave Clock Stretch Maximum Cycles
Clock cycles in slave maximum clock stretch count. Prescaled by SMBTR.EXP. Used to time T
LOW:SEXT
.
31 30 29 28 27 26 25 24
EXP ----
23 22 21 20 19 18 17 16
THMAX
15 14 13 12 11 10 9 8
TLOWM
76543210
TLOWS
f
prescaled SMBus,
f
CLKTWIM
2
EXP 1+()
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=