Am186™CC/CH/CU Microcontrollers User’s Manual
4-1
CHAPTER
4
EMULATOR SUPPORT
4.1
OVERVIEW
This chapter describes the various features available in the Am186CC/CH/CU
microcontrollers to facilitate the design and operation of an In-Circuit Emulator (ICE). Most
of the discussion centers around the operation of pins. Because different debug tool
manufacturers take different approaches to emulator implementation, restrictions imposed
by the use of one type of emulator may not apply to another. However, there are a number
of common concerns shared among ICE developers. This chapter discusses those
concerns.
4.2
SYSTEM DESIGN
The main issues to consider are multiplexed pin use and emulator connection.
4.2.1
Multiplexed Pins
Because pins are an expensive resource, many of the pins on the Am186CC/CH/CU
microcontrollers serve more than one purpose. These multiplexed pins enable the system
designer to select, by hardware or software means, the required operation of the pin. It can
often be difficult for an emulator to know the function of such multiplexed pins, particularly
if the system modifies pin operation on-the-fly. Therefore, before committing a design to
hardware, the system designer should contact potential emulator suppliers for a list of
emulator pin requirements.
Certain pins are critical for successful emulator operation; these are address pins, chip
selects, and memory access timing signals. It is important that these pins not be multiplexed
in such a way as to compromise the emulator operation. Fortunately, several pin functions
can be successfully multiplexed. Emulators generally do not monitor pins relating to input/
output (PIO) operation and on-chip peripherals.
The Am186CC/CH/CU microcontrollers were designed to minimize conflicts. In most cases,
pin conflict is avoided. For example, if the Address Latch Enable (ALE) signal is required
for multiplex bus support, then it is not programmed as PIO33. If the multiplexed AD bus is
used for data only (not addresses), then ALE can be programmed as a PIO pin and the
emulator will not require the ALE signal. However, an emulator is likely to always use the
de-multiplexed address, regardless of how the AD bus is programmed.
The following PIO signals are multiplexed with alternate signals that may be used by
emulators: PIO8, PIO15, PIO33, PIO34, and PIO35. Consider any emulator requirements
for the alternate signals before using these pins as PIOs.
4.2.2
Emulator Connection
Several package types present emulation problems. At the time of publication, the
Am186CC/CH/CU microcontrollers ship in 160-pin PQFP packages.
When a PQFP device is soldered to a board, it cannot be removed and replaced with an
emulator. In this situation, the CPU must be disabled somehow, and the emulator must be
connected to the CPU to duplicate its functionality. The Am186CC/CH/CU microcontrollers
do this with the On-Circuit Emulation (ONCE) mode. Placing the microcontroller in ONCE
mode causes the output pins to become three-state and inactive. This feature allows a
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...