Semiconductor Group
6-42
1999-04-01
On-Chip Peripheral Components
C541U
6.4.2.3
Dual Buffer Mode
In dual buffer mode, both USB memory pages (page 0 and page 1) are used for data transfers. The
logical assignment of the memory pages to CPU or USB is automatically switched. The following
two figures show the buffer handling concept in dual buffer mode for the USB read access and USB
write access.
Figure 6-25
USB Read Access in Dual Buffer Mode - Buffer Handling
CPU Buffer Handling
CPU page is empty : CBF = 0
CPU write access enabled
CPU writes 1 Byte
CPU buffer
full?
CPU buffer is full : CBF = 1
CPU write access disabled
Pages are (CBF = 1 and UBF = 0)
EOD = 1
USB page
empty?
SOD = 1
Yes
Yes
No
No
No
Yes
Yes
full?
CPU page
USB read access disabled
USB buffer is empty: UBF = 0
request?
USB read
USB reads buffer
USB read access enabled
USB page is full : UBF = 1
USB Buffer Handling
No
MCB03405
swapped
Summary of Contents for C541U
Page 1: ... 8 LW 026 0LFURFRQWUROOHU 8VHU V 0DQXDO http www siem ens d Sem iconductor ...
Page 7: ......
Page 21: ...Semiconductor Group 2 6 1997 10 01 Fundamental Structure C541U ...
Page 37: ...Semiconductor Group 4 6 1997 10 01 External Bus Interface C541U ...
Page 133: ...Semiconductor Group 6 88 1999 04 01 On Chip Peripheral Components C541U ...
Page 163: ...Semiconductor Group 8 8 1997 10 01 Fail Safe Mechanisms C541U ...
Page 185: ...Semiconductor Group 10 14 1997 10 01 OTP Memory Operation C541U ...