DRAM Controller
6-4
Am186™CC/CH/CU Microcontrollers User’s Manual
6.5.3
DRAM Interface
The microcontroller provides zero-wait state operation at up to 50 MHz with 40-ns DRAM.
Internal wait states can be inserted to support slower DRAM; however, external ready
detection is not supported. All signals required by the DRAM are generated on the
microcontroller and no external logic is required.
The DRAM multiplexed address pins are connected to the odd address pins starting with
A1 on the microcontroller to MA0 on the DRAM (see Table 6-4). The correct row and column
addresses are generated on these pins during a DRAM access. Table 6-4 shows how the
physical address bits are mapped to row and column addresses on external pins.
The CAS0 and CAS1 signals select which byte of the DRAM is accessed during a read or
write. The RAS0 signal controls the lower bank of DRAM, which starts at 00000h in the
address map and is bounded by the ending address selected with the UB bit field in the
LMCS register. The RAS1 signal controls the upper bank of DRAM, which ends at FFFFFh
and is bounded by the starting address selected in the LB bit field in the UMCS register.
When RAS1 is asserted, UCS is automatically deasserted. Neither, either, or both DRAM
banks can be activated.
Table 6-3
DRAM Supported by the Am186CC/CH/CU Microcontrollers
CPU Clock
Speed
DRAM Speed
Wait States
Refresh
Cycles
25 MHz
50 ns
0
7 clocks
60 ns
7 clocks
70 ns
7 clocks
40 MHz
50 ns
0
7 clocks
60 ns
1
7 clocks
70 ns
2
7 clocks
50 MHz
40 ns
0
7 clocks
50 ns
1
7 clocks
60 ns
2
7 clocks
70 ns
3
7 clocks
Table 6-4
Address Multiplexing Reference
Am186CC/CH/CU
Address Pin
DRAM
Address Pin
Row
Column
A1
MA0
PA1
PA2
A3
MA1
PA3
PA4
A5
MA2
PA5
PA6
A7
MA3
PA7
PA8
A9
MA4
PA9
PA10
A11
MA5
PA11
PA12
A13
MA6
PA13
PA14
A15
MA7
PA15
PA16
A17
MA8
PA17
PA18
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...