System Overview
3-32
Am186™CC/CH/CU Microcontrollers User’s Manual
3.6.3.6
DRAM Controller
The microcontroller has a fully integrated DRAM controller that provides a glueliss interface
to 25-ns–70-ns EDO DRAM. The microcontroller provides zero-wait state operation at up
to 50 MHz with 40-ns DRAM. The DRAM controller includes the following features:
■
Multiplexed addresses for DRAM row and column accesses
■
8-bit and 16-bit boot mode for UCS accesses
■
Two RAS signals that support two banks of DRAM
■
Two byte CAS signals
■
Direct support for 4-Mbit (256Kx16) extended data out (EDO) DRAMs
■
Prioritized PCS over DRAM space accesses
The various cycles in the microcontroller follow this priority ranking: refresh (highest priority),
HOLD, DMA, and CPU (lowest).
For more information about DRAM, see Chapter 6, “DRAM Controller.”
3.7
CLOCK CONTROL
The microcontroller clocks include the general system clock (CLKOUT), and the baud rate
generator clock for the two Universal Asynchronous Receiver Transmitters (UART and high-
speed UART). The Synchronous Serial Interface (SSI) and the timers (Timers 0, 1, and 2)
derive their clocks from the system clock.
3.7.1
Clock Features
The microcontroller includes the following clock features and characteristics. Figure 3-3
illustrates the clocks. For detailed information on the clocks, see the data sheets for
Am186CC/CH/CU microcontrollers.
■
One crystal-controlled oscillator that uses an external fundamental mode crystal or
oscillator to generate the system input clock.
■
One internal PLL that generates a system clock (CLKOUT) that is 1x, 2x, or 4x the
system input clock.
■
SSI clock (SCLK) is derived from the system clock, divided by 2, 4, 8, 16, 32, 64, 128,
or 256.
■
Timers 0 and 1 can be configured to be driven by the timer input pins (TMRIN1, TMRIN0)
or at one-fourth of the system clock. Timer 2 is driven at one-fourth of the CPU clock.
■
UART clock can be derived from the internal system clock frequency or from the UART
clock (UCLK) input.
The Am186CC and Am186CU microcontrollers also include the Universal Serial Bus (USB)
clock with the following features:
■
One independent crystal-controlled oscillator that uses an external fundamental mode
crystal or oscillator to generate the USB input clock.
■
One internal PLL that generates the 48-MHz clock required for the USB from either a
24-MHz or 12-MHz input.
■
Single clock source operation possible by sharing the clock source between the system
and the USB.
CU
CC
Содержание Am186 CC
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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...
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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...