System Overview
3-6
Am186™CC/CH/CU Microcontrollers User’s Manual
During an external reset, RESOUT remains active (High) for two clocks after RES is
deasserted. The microcontroller exits reset and begins the first valid bus cycle
approximately 4.5 clocks after RES is deasserted.
With an internal reset, the watchdog timer reset duration, and therefore the duration of the
RESOUT signal, is 2
16
processor clocks. This duration allows sufficient time for external
devices to reach their reset state. For more information about internal resets, see
Chapter 11, “Watchdog Timer.”
Both external and internal resets set the registers to predefined values as shown in
Appendix A, “Register Summary,” with the exception of the RESCON and WDTCON
registers whose default values depend on the type of reset.
The Reset Configuration (RESCON) register latches system-configuration information that
is presented to the processor on the address/data bus (AD15–AD0) at the deassertion of
RES. The interpretation of this information is system-specific. The processor does not
impose any predetermined interpretation, but simply provides a means for communicating
this information to software. When the RES input is asserted, the contents of the AD bus
are written into the RESCON register. Note that the RESCON value is only sampled on an
external reset. The system can place configuration information on the AD bus using weak
external pullup or pulldown resistors, or using an external driver that is enabled during reset.
The processor does not drive the AD bus during reset. For example, the RESCON register
could be used to provide the software with the position of a configuration switch in the
system. By using weak external pullup and pulldown resistors on the AD bus, the system
could provide the microcontroller with a value corresponding to the position of a jumper
during reset.
For compatibility with future devices, always write reserved bits in registers with their reset
default values. The
Am186™CC/CH/CU Microcontrollers Register Set Manual, order
#21916, defines the bits for all the registers.
Table 3-4
CPU and Internal Peripheral States Immediately Following Power-On Reset
CPU/Peripheral
State
Am186 CPU
Enabled, executes at address FFFF0h
Chip Selects
UCS active, all other chip selects inactive
DRAM Controller
Disabled
Interrupt Controller
Disabled—only nonmaskable interrupts and traps can
be taken
General-Purpose DMA and SmartDMA Channels
Disabled
Programmable I/Os
See Chapter 9, “Programmable I/O Signals”
Programmable Timers
Disabled
Watchdog Timer
Enabled with maximum time-out value (2
16
clocks)
UART and High-Speed UART
Disabled
Synchronous Serial Interface (SSI)
Disabled
High-level Data Link Control (HDLC) Channels
Disabled
Time Slot Assigners (TSAs)
Disabled
General Circuit Interface (GCI)
Disabled
Universal Serial Bus (USB) Peripheral Controller
Disabled
CC
CH
CC
CH
CC
CC
CU
Содержание Am186 CC
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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...