Datasheet

Table 24. Conversion Results Registers Description (continued)
READ ONLY
ADDRESS
NAME DESCRIPTION
E2h TOF_DIFFInt
16-bit xed-point two’s-complement integer portion of the difference of the averages for the hits
recorded in both the upstream and downstream directions. It is computed as:
AVGUP – AVGDN
This integer represents the number of t
4MHz
periods that contribute to computation. The
maximum size of the integer is 7FFFh or (2
15
– 1) x t
4MHz
. The minimum size of this integer is
8000h or -2
15
x t
4MHz
.
E3h
TOF_
DIFFFrac
16-bit fractional portion of the two’s complement difference of the averages for the hits
recorded in both the upstream and downstream directions. This fractional portion is a binary
representation of one t
4MHz
period quantized to a 16-bit resolution. The maximum size of the
fraction is FFFFh or (2
16
- 1)/2
16
x t
4MHz
.
E4h
TOF_Cycle_
Count
/TOF_Range
Bit 15 through bit 8 holds the 8-bit value of the TOF_Range. The TOF_Range is an 8-bit binary
integer that indicates the range of valid error-free TOF_DIFF measurements that were made
during execution of either of the EVTMG1 or EVTMG2 commands. The maximum value of
TOF_Range is equal to 2 times the actual pulse launch period as congured by the pulse launch
divider bits in the TOF1 register.
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8
MSB TOF_Range 8-bit binary integer LSB
The formulas to calculate the range and resolution of the TOF_Range integer for a given
DPL[3:0] bit setting are shown below:
Maximum range (µs) = DPL[3:0] + 1 Resolution = Maximum range/256
DPL[3:0]
LAUNCH
FREQUENCY
MAXIMUM RANGE
(µs)
RESOLUTION
(ns)
0001b 1MHz 2 7.8175
0002b 666.6kHz 3 11.7185
…. …. …. ….
1110b 133.3kHz 15 58.59375
1111b 125kHz 16 62.5
Bit 7 through bit 0 holds the 8-bit value of the TOF cycle count. The TOF cycle count is an 8-bit
binary integer that indicates the number of valid error-free cycles that either of the EVTMG1 or
EVTMG2 commands has executed. It also represents the number of TOF_DIFF cycles that have
been totaled for the purpose of averaging, which affects the results provided in the TOF_DIFF_
AVGFrac and TOF_DIFF_AVGInt registers. It is incremented every time an error-free TOF_DIFF
command is executed by either the EVTMG1 or EVTMG2 sequence. Because of this internal
error checking, once the complete number of cycles dened by the TOF difference masurements
bits in the Event Timing 1 register has been completed and the TOF_EVTMG bit has been set
in the Interrupt Status register causing the INT device pin to be asserted (if enabled), the TOF
Cycle Count may not be equal to the setting of the TOF difference measurements bits in the
Event Timing 1 register.
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
MSB TOF cycle count 8-bit binary integer LSB
MAX35101 Time-to-Digital Converter with Analog Front-End
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