DMA Controller
Am186™CC/CH/CU Microcontrollers User’s Manual
8-11
or Circular Buffers” on page 8-20. This method helps guarantee data integrity by ensuring
that data is transferred to main memory whether or not the interrupt task can execute. The
DMA channel can be set to interrupt immediately on receipt of data by setting the Interrupt
(INT) and Terminal Count (TC) bits in the GDxCON0 register. The interrupt task is then a
relatively low priority because it does not have to pull the characters out of the UART before
they are overwritten by new data. (The effective UART FIFO size has been increased by
the DMA buffer size.) When the interrupt task has finished processing all the data in the
circular buffer (its read pointer is equal to the destination address), the interrupt can set TC
to cause another interrupt as soon as additional characters arrive.
Processing the received data within a low-priority interrupt routine means that flow-control
information, such as XONs and XOFFs, may not be seen as quickly. To alleviate this
condition, transmission can be done without using DMA (e.g., from within the same interrupt
routine, or by programming the interrupt code). In the latter, the interrupt code could program
the Transfer Count (GDxTC) register to send a maximum of n characters at a time, using
DMA, where '2 • n' is a value that does not overrun the far side's receive FIFO high-water
mark.
8.5.6
General-Purpose DMA Channels
The Am186CC/CH/CU microcontrollers each provide four general-purpose DMA channels,
which are similar to legacy Am186 general-purpose DMA channels. The four channels can
be used for data transfers as shown in Table 8-6.
Table 8-6
General-Purpose DMA Data Transfers
Source
Destination
Memory
Memory
I/O
Internal peripherals:
UART
High-Speed UART
USB
External peripherals
I/O
Memory
I/O
Internal peripherals:
UART
High-Speed UART
USB
External peripherals
Internal Peripherals:
Timer 2
1
UART
High-Speed UART
USB
Notes:
1. Timer 2 acts as a DMA request source only; no data is transferred to or from Timer 2.
Memory
I/O
External Peripherals
Memory
I/O
CC
CU
CC
CU
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...