TMD4903 Datasheet, PDF (61/86 Pages) ams AG – Color and Proximity Sensor Module with mobeam

TMD4903 − Application Information
Figure 72:
Timeword RAM Table
T_INDEX
0
1
2
3
~
15
Timeword RAM
The Timeword RAM is a dedicated table that contains sixteen,
16-bit words which are used to set pulse and gap widths. The
pulse and gap widths are described as a multiple of carrier
periods, T_CAR. For example, if the LED must modulate for 8
carrier periods, then be off for 15 carrier periods, index 0 could
be loaded with 0x0008 and index 1 could be loaded with
0x000F. A pattern RAM value of 0x01 would result in LED
activation for 8 T_CARs, as stored in index 0, and a LED
deactivation for 15 T_CARs.
Similarly to pattern RAM, the Timeword table also has a special
operator. If the timeword value is zero, then whatever state the
LED was in last (I.e. modulating or deactivated) will be
continued into the next pulse or gap defined in pattern RAM.
For example, if the RAM Pulse nibble (MSB) indexes a timeword
set to 5, and the gap (LSB) nibble indexes a timeword set to 0,
the LED will modulate for 5T_CARs then instead of deactivating,
the modulation is continued into the next pulse in pattern RAM.
In this way pulses or gaps longer than 65535 T_CARs can be
generated.
T_DATA
0 to 65535
0 to 65535
0 to 65535
0 to 65535
~
0 to 65535
Timeword RAM
I²C Address (Bank 1)
0x01 8-bit MSB
0x03 8-bit MSB
0x05 8-bit MSB
0x07 8-bit MSB
~
0x0F 8-bit MSB
0x00 8-bit LSB
0x02 8-bit LSB
0x04 8-bit LSB
0x06 8-bit LSB
~
0x1E 8-bit LSB
Timeword RAM: Volatile memory used for storing 16-bit timing data.
The Timeword table is located in RAM bank two. Each 16-bit
word is accessible using two byte locations: MSB bytes are
stored in even addresses and LSBs are stored in odd addresses.
For example, if 0x2953 is to be stored at index 0, then 0x29 is
written to: bank 2, I²C address of 0x00, and 0x53 is written to
bank 2, I²C address of 0x01.
ams Datasheet
[v1-12] 2015-May-14
Page 61
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