Am186™CC/CH/CU Microcontrollers User’s Manual
6-1
CHAPTER
6
DRAM CONTROLLER
6.1
OVERVIEW
Dynamic Random Access Memory (DRAM) offers memory at moderate speed and low
cost. DRAM memory cells consist of one transistor and one capacitor. DRAM also uses a
multiplexed address bus in a row/column format, which results in a lower pin count and
smaller device package.
DRAM is volatile; that is, if the capacitors for the memory cells are not periodically recharged,
the contents of memory is lost. The process of periodically recharging the capacitors is
called refresh.
The DRAM controller’s purpose is to use the processor’s address, status, and control lines
to generate the multiplexed address strobes. The Row Address Strobe (RAS) and Column
Address Strobe (CAS) signals latch the row and column addresses inside the DRAM.
To support DRAM, the Am186CC/CH/CU microcontrollers each have a fully integrated
DRAM controller that provides a glueless interface to 40-ns, 50-ns, 60-ns, and 70-ns
Extended Data Out (EDO) DRAM (EDO DRAM is sometimes called Hyper-Page Mode
DRAM). Up to two banks of 4-Mbit (256 Kbit x 16 bit) DRAM can be accessed. Page Mode,
Fast Page Mode (FPM), Asymmetrical, and 8-bit wide DRAM are not supported.
The Am186CC/CH/CU microcontrollers support the most common DRAM refresh option,
CAS-Before-RAS. All refresh cycles contain three wait states to support the DRAMs at
various frequencies. The DRAM controller never performs a burst access. All accesses are
single accesses to DRAM. If the PCS chip selects are decoded to be in the DRAM address
range, PCS accesses take precedence over the DRAM.
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...