OMAP L138 RTC: capacitors needed with crystal?

Hi,

I would like to ask a question with L138 RTC module.

Are external capacitors required along with crystal?

In SPRS586C OMAP-L138 C6-Integra DSP+ARM Processor Technical Reference Manual:

Not required

1. §5.31.1, p.260: "direct operation" with a crystal
2. §5.31, Fig. 5-84, no capacitor is drawn

Required

1. §5.31.1, Fig.5-85, two capacitors are drawn
2. EVMAM1808 schematics sheet 13, two capacitors are used

There exist devices whose clock module contain internal adjustable capacitor that eliminates the need of external capacitor. The "direct operation" seems to suggest this. But is this true? Can external capacitors be removed?

Zheng