TMD49037 datasheet(62/86 Pages) OSRAM

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[v2-00] 2022-Nov-03

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TMD4903 − Application Information

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, TCAR. 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 TCARs, as stored in index 0, and a LED

deactivation for 15 TCARs.

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 5TCARs then instead of deactivating,

the modulation is continued into the next pulse in pattern RAM.

In this way pulses or gaps longer than 65535 TCARs can be

generated.

Figure 72:

Timeword RAM Table

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.

Timeword RAM

T_INDEX

T_DATA

I2C Address (Bank 1)

0 to 65535

0x01 8-bit MSB

0x00 8-bit LSB

0 to 65535

0x03 8-bit MSB

0x02 8-bit LSB

0 to 65535

0x05 8-bit MSB

0x04 8-bit LSB

0 to 65535

0x07 8-bit MSB

0x06 8-bit LSB

0 to 65535

0x0F 8-bit MSB

0x1E 8-bit LSB

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