Emulator Support
4-2
Am186™CC/CH/CU Microcontrollers User’s Manual
designer to clip an emulator pod over the target CPU, then use ONCE mode to disable the
target CPU and provide a connection to each of the PQFP processor pins. Be aware of any
horizontal and vertical areas required by the emulators’ physical attachment method, and
plan the board layout accordingly. One common mistake is to place connectors, switches,
or other board controls under an area that will be partially covered by the emulator target
board. Also consider the arrangement of Pin 1 versus the emulator attachment and plan
accordingly.
4.3
OPERATION
4.3.1
Usage
To use an emulator, the microcontroller must be put into ONCE mode. To enter ONCE
mode, use the ONCE reset configuration pin (pinstrap). ONCE is sampled on the rising
edge of RES. If the ONCE pin is asserted, the microcontroller enters ONCE mode.
Otherwise, it operates normally. In ONCE mode, all pins are three-stated and remain that
way until a subsequent reset occurs. To ensure the microcontroller does not inadvertently
enter ONCE mode, ONCE has a weak internal pullup resistor that is active only during an
external reset.
Note: Before using an emulator, ensure multiplexed pins are configured to reflect the use
of the emulator and not other functionality.
4.3.2
Emulator-Related Signals
4.3.2.1
A19–A0
To facilitate emulation, the Am186CC/CH/CU microcontrollers do not multiplex any of the
A19–A0 address pins. Therefore, these pins are always available for emulation.
4.3.2.2
AD15–AD0
The Am186CC/CH/CU microcontrollers do not multiplex any AD15–AD0 address/data pins
with other functionality, except that the value present on AD15–AD0 as the device comes
out of external reset is latched and saved internally to the Reset Configuration (RESCON)
register. Using this mechanism, a set of weak pullups and pulldowns can be put on the bus
to allow hardware to communicate configuration information to the software. Because this
is an input function, it should not interfere with the operation of the emulator. However, the
emulator should not interfere with the value present at reset, as software may be relying
on the value for proper operation.
4.3.2.3
{ADEN} / BHE
Deasserting ADEN on reset can prevent the multiplexed AD bus from providing address
information for lower (LCS) and upper (UCS) memory regions. Some older ICE designs
force ADEN active to force address information on the AD bus. System designers should
be aware if their emulator uses this operation and any conflicts this can cause with their
hardware.
186 processors use BHE along with A0 to determine the type and width of external bus
accesses. 188’s do not have BHE, because all data on a 188 is 8 bits wide and routed
through AD7–AD0. The Am186CC/CH/CU microcontrollers do not support a 188 version,
but do allow defining memory regions as 8-bit memory. When making accesses to 8-bit
wide memory regions, BHE cannot be used to derive any information about the access.
Use the BSIZE8 signal to determine the width of a memory region unambiguously.
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...