Emulator Support
4-4
Am186™CC/CH/CU Microcontrollers User’s Manual
4.3.2.11
MCS3–MCS0
The system uses MCS1 and MCS2 as DRAM CAS strobes. MCS0 and MCS3 can be used
as extra memory chip selects. Emulators can use these to determine when accesses occur
to these memory spaces, and can intercept it for overlay memory purposes.
4.3.2.12
{ONCE}
ONCE is not a dedicated pin but rather a pinstrap option that allows an external emulator
to place a target device into On-Circuit Emulation mode. On reset of the microcontroller, if
the ONCE pinstrap is held low, all Am186CC/CH/CU pins enter a high-impedance state.
There is an internal pullup to prevent inadvertent assertion of ONCE.
4.3.2.13
QS1–QS0
The Am186CC/CH/CU microcontrollers provide information about the execution queue on
the Queue Status bus, QS1–QS0. These signals assist in disassembling trace buffer
information.
4.3.2.14
[RAS1–RAS0]
See “[CAS1–CAS0] and [RAS1–RAS0]” on page 4-3.
4.3.2.15
RD
The RD strobe can be intercepted by the emulator for use with overlay memory.
4.3.2.16
RES
The Am186 processor family provides a Schmitt trigger on the RES input to enable the
system designer to use an inexpensive RC circuit to provide system reset. The only
restriction on power-up is for RES to stay active (Low) for at least 1 ms. Systems that use
this feature introduced a problem for In-Circuit Emulators because emulators need to know
when the target processor comes out of reset. This can be difficult to determine when the
target is being placed in ONCE mode and the reset signal has a very slow rise time. Emulator
vendors solve this problem by providing a reset signal with a fast rise time. The hardware
designer must use this emulator-supplied reset instead of the standard RC reset circuit.
The Am186CC/CH/CU microcontrollers provide a RESOUT signal that unambiguously
indicates when the device has come out of reset, eliminating this problem. However, many
emulators still generate a target reset (in response to a user console command, for
instance), and therefore need a means to connect the emulator-supplied reset to the target
hardware.
Therefore, if ICE usage is required, be aware of the emulators’ reset requirements and take
them into consideration when designing the target hardware, typically by providing a
convenient means to allow the emulator-supplied reset to be the main system reset.
4.3.2.17
RESOUT
RESOUT is activated by the Am186CC/CH/CU microcontrollers in response to either RES
being held active, or a system reset being generated by the internal watchdog timer. During
reset, this pin is actively driven, regardless of the state of the ONCE mode pinstrap (in
contrast, all other output pins go to three-state if both RES and ONCE are active). When
RES is deasserted, RESOUT is driven inactive. This high-to-low edge on RESOUT is the
signal that latches the value of all pinstrap options. When ONCE is active and RES is
inactive, RESOUT is driven inactive (all other outputs are three-stated), and held Low for
one clock cycle. After this one-clock period, RESOUT is three-stated. This sequence of
events allows an attached emulator to determine with certainty that the device has entered
ONCE mode.
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...