DMA Controller
8-38
Am186™CC/CH/CU Microcontrollers User’s Manual
5. If the terminal count reaches zero before the end-of-packet signal from the device is
asserted, the receiver closes the current buffer and enters Get-Next-Buffer mode. In this
mode, the receiver reads the next descriptor in the descriptor ring and determines if the
OWN bit is set. If the OWN bit is 0, the receiver remains in Get-Next-Buffer mode,
periodically polling the descriptor, until the OWN bit becomes set. When the OWN bit is
detected as set, the receiver loads the buffer address and terminal count from the new
descriptor and returns to normal-receive mode.
6. When the receiver detects the end-of-packet signal from the device, the receiver moves
to Receive-End mode. In Receive-End mode, the receiver reads the status information
from the device and writes it to the descriptor. The end-of-packet bit is set in the descriptor
and the OWN bit is cleared. If RXS0 is set, the EOP bit is set but the OWN bit not cleared.
7. The receiver advances the descriptor ring pointer and enters Initialize mode.
8.5.7.6
SmartDMA Channel Descriptor Format
Each entry in the descriptor ring consists of four 16-bit words. Table 8-13 shows the format
of the transmit descriptor ring; Table 8-14, the receive descriptor ring.
Figure 8-9
SmartDMA Receive Channel Flow Diagram
Initialize channel
Receive data
Get next buffer
Owner
semaphore
set
Signal end of
OWN=0
OWN=1
ENP=0
ENP=1
receive
Search for
available buffer
OWN=1
OWN=1
Receive byte
and decrement
count
(TC=0)
(TC=0)
(TC>0)
Notes:
The TC bit is internal and not seen by users.
Owner semaphore bit not set
Owner
semaphore
bit set
Owner
semaphore
bit set
Terminal
count and
end-of-packet
Terminal
count and not
end-of-packet
Write status, clear
owner semaphore bit,
and advance to next
descriptor.
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...