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.
Содержание Am186 CC
Страница 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Страница 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Страница 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Страница 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Страница 39: ...Architectural Overview Am186 CC CH CU Microcontrollers User s Manual 1 15 Figure 1 6 32 Channel Linecard CH CC...
Страница 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Страница 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Страница 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Страница 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Страница 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Страница 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Страница 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Страница 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Страница 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...