System Overview
Am186™CC/CH/CU Microcontrollers User’s Manual
3-7
Table 3-5
Reset Configuration Pins (Pinstraps)
1
Notes:
1. A pinstrap is used to enable or disable features based on the state of the pin during an external reset. The pinstrap must be
held in its desired state for at least 4.5 clock cycles after the deassertion of RES. The pinstraps are sampled in an external
reset only (when RES is asserted), not during an internal watchdog timer-generated reset.
Signal Name
Multiplexed
Signal(s)
Description
{ADEN}
BHE
PIO34
Address Enable: If {ADEN} is held High or left floating during power-on reset, the
address portion of the AD bus (AD15–AD0) is enabled or disabled during LCS, UCS,
or other memory bus cycles based on how the software configures the DA bit in the
UMCS or LMCS registers. In this case, the memory address is accessed on the A19–
A0 pins. There is a weak internal pullup resistor on {ADEN} so no external pullup is
required. This mode of operation reduces power consumption.
If {ADEN} is held Low on power-on reset, the AD bus drives both addresses and data,
regardless of how software configures the DA bit in the UMCS or LMCS registers.
{CLKSEL1}
{CLKSEL2}
HLDA
[PCS4]
PIO3
CPU PLL Mode Select 1 determines the PLL mode for the CPU clock source.
CPU PLL Mode Select 2 is sampled on the rising edge of reset and determines the
PLL mode for the CPU clock source. This pin has an internal pullup resistor that is
active only during reset. There are four CPU PLL modes that are selected by the
values of {CLKSEL1} and {CLKSEL2} as shown below.
{ONCE}
UCS
ONCE Mode Request asserted Low places the Am186CC/CH/CU microcontroller
into ONCE mode. Otherwise, the controller operates normally. In ONCE mode, all
pins are three-stated and remain in that state until a subsequent reset occurs. To
guarantee that the controller does not inadvertently enter ONCE mode, {ONCE} has
a weak internal pullup resistor that is active only during a reset. A reset ending ONCE
mode should be as long as a power-on reset for the PLL to stabilize.
{UCSX8}
[MCS0]
PIO4
Upper Memory Chip Select, 8-Bit Bus asserted Low configures the upper chip
select region for an 8-bit bus size. This pin has a pullup resistor that is active only
during reset, so no external pullup is required to set the bus to 16-bit mode.
{USBSEL2}
{USBSEL1}
PCS1
PIO14
PCS0
PIO13
USB Clock Mode Selects 1–2 select the USB PLL operating mode. The pins have
internal pullups that are active only during reset. The USB PLL can operate in one
of three modes. With a crystal and the internal USB oscillator or an external oscillator,
the USB PLL can output 4X or 2X the input frequency. The USB PLL can also be
disabled and the USB peripheral controller can receive its clock from the CPU PLL,
which is the default mode. The pins are encoded as shown below.
{USBXCVR}
S0
USB External Transceiver Enable asserted Low disables the internal USB trans-
ceiver and enables the pins needed to hook up an external transceiver. This pin has
a pullup resistor that is active only during reset, so no external pullup is required as
long as the user ensures that this input is not driven Low during a power-on reset.
CPU PLL Modes
{CLKSEL1}
{CLKSEL2}
CPU PLL Mode
1
1
2X, CPU PLL enabled (default)
1
0
4X, CPU PLL enabled
0
1
1X, CPU PLL enabled
0
0
PLL Bypass
CC
CU
CC
CU
USB PLL Modes
{USBSEL1}
{USBSEL2}
USB PLL Mode
1
1
Use CPU clock (after CPU PLL mode
select), USB PLL disabled (default)
1
0
4X, USB PLL enabled
0
1
2X, USB PLL enabled
0
0
Reserved
CC
CU
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...