您好，请教如下问题，望回答，谢谢！
Code Path: C:CypressUSBExamplesFX2LPBulkloopBulkloop.C
// default: all endpoints have their VALID bit set
// default: TYPE1 = 1 and TYPE0 = 0 --> BULK
// default: EP2 and EP4 DIR bits are 0 (OUT direction)
// default: EP6 and EP8 DIR bits are 1 (IN direction)
// default: EP2, EP4, EP6, and EP8 are double buffered (1)
// we are just using the default values, yet this is not necessary...
EP1OUTCFG = 0xA0; (2)
EP1INCFG = 0xA0;
SYNCDELAY; // see TRM section 15.14
EP2CFG = 0xA2;
SYNCDELAY;
EP4CFG = 0xA0;
SYNCDELAY;
EP6CFG = 0xE2;
SYNCDELAY;
EP8CFG = 0xE0;
// out endpoints do not come up armed
// since the defaults are double buffered we must write dummy byte counts twice (3)
SYNCDELAY;
EP2BCL = 0x80; // arm EP2OUT by writing byte count w/skip.
SYNCDELAY;
EP2BCL = 0x80;
SYNCDELAY;
EP4BCL = 0x80; // arm EP4OUT by writing byte count w/skip.
SYNCDELAY;
EP4BCL = 0x80;
问题：
(1)从下面寄存器看，只有2&6是Double Buffer，为什么说4&8也是Double Buffer？
贴不上图，请看ez_usb_r___technical_reference_manual__trm__14 P262
(2)
EP1OUTCFG = 0xA0;
EP1INCFG = 0xA0;
这两个寄存器之间为什么不用加 SYNCDELAY;
(3) “since the defaults are double buffered we must write dummy byte counts twice”
请问这句话的依据是什么？在Datasheet的什么地方可以看到这句话的原型？
另外，为什么只写EP2BCL & EP4BCL，不写EP6BCL & EP8BCL ？
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