DMA Controller
8-40
Am186™CC/CH/CU Microcontrollers User’s Manual
Table 8-14
SmartDMA Receive Channel Descriptor Format
Bit Number
Bit Name
Description
Receive Buffer Address (Word 0)
15–0
LADR
1
The LADR (Low Order) field contains the 16 low order address bits of the data buffer
pointed to by this descriptor. The LADR field is written by the software and not
changed by the SmartDMA channel.
Receive Buffer Status/Config (Word 1)
15
OWN
0 = Descriptor entry is owned by the software.
1 = Descriptor entry is owned by the SmartDMA channel.
The SmartDMA channel clears the OWN bit (unless the RXS0 bit is set) after filling
the buffer pointed to by this descriptor. The software sets the OWN bit after emptying
the buffer. Neither the software nor the SmartDMA channel can alter a descriptor
entry after it has relinquished ownership.
14
ERR
The ERR (Error Summary) bit is the logical OR of FRAM, OFLO, CRC and HBUF.
13
FRAM
The FRAM (Framing Error) bit indicates that the received frame did not contain a
multiple of eight bits. The CRC bit is not checked when the FRAM bit is set. The
FRAM bit is valid only when the ENP bit is set and the OFLO bit is not. This bit is not
used when the USB is the receive request. This bit is cleared by software.
12
OFLO
The OFLO (Overflow Error) bit indicates that the internal receive FIFO has detected
an overflow condition. The OFLO bit is valid only when the ENP bit is not set. This
bit is cleared by software.
11
CRC
The CRC (Cyclic Redundancy Check Error) bit indicates:
•
When HDLC is the requesting source, the current frame has a CRC error.
•
When USB is the requesting source, one of the following errors occurred:
•
If the USB endpoint type is BULK, the possible errors are: CRC, bit stuff, more
than max packet value sent by software, data PID error, or data toggle error.
•
If USB endpoint type is ISO, the possible errors are: CRC, bit stuff, more than
max packet value sent by software, or data PID error.
The CRC bit is valid only when the ENP bit is set and the OFLO bit is not. This bit is
cleared by software.
10
HBUF
The HBUF (Buffer Error) bit indicates that the current frame has one of the following
errors:
•
Frame ended in an abort instead of a flag.
•
Frame length was longer than the maximum length allowed. In this case, the MCNT
field is equal to the maximum length allowed.
•
Frame length was shorter than the minimum allowed. Part of the data of the frame
was already discarded in the receiver. The MCNT field indicates the number of
bytes that were output by the FIFO, not the number of bytes in the frame.
This bit is not used when the USB is the receive request.
This bit is cleared by the software.
9
STP
The STP (Start of Packet) bit indicates that this is the first buffer used by the
SmartDMA channel for this packet. It is used to chain data buffers. The STP bit is set
by the SmartDMA channel.
8
ENP
The ENP (End of Packet) bit indicates that this is the last buffer used by the SmartDMA
channel for this packet. It is used to chain data buffers. If both the STP bit and the
ENP bit are set, the packet fits into one buffer and there is no data chaining. The ENP
bit is set by the SmartDMA channel.
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...