AM186 Datasheet, PDF (38/112 Pages) Advanced Micro Devices – High-Performance, 80C186- and 80C188-Compatible, 16-Bit Embedded Microcontrollers with RAM

SRDY/PIO6
UCS/ONCE1
Synchronous Ready (input, synchronous,
level-sensitive)
Upper Memory Chip Select (output, synchronous)
ONCE Mode Request 1 (input, internal pullup)
This pin indicates to the microcontroller that the ad- UCS—This pin indicates to the system that a memory
dressed memory space or I/O device will complete a access is in progress to the upper memory block. The
data transfer. The SRDY pin accepts an active High base address and size of the upper memory block are
input synchronized to CLKOUTA.
programmable up to 512 Kbyte. UCS is held High dur-
Using SRDY instead of ARDY allows a relaxed system
ing a bus hold condition.
timing because of the elimination of the one-half clock After power-on reset, UCS is asserted because the mi-
period required to internally synchronize ARDY. To al- crocontroller begins executing at FFFF0h and the de-
ways assert the ready condition to the microcontroller, fault configuration for the UCS chip select is 64 Kbyte
tie SRDY High. If the system does not use SRDY, tie the from F0000h to FFFFFh.
pin Low to yield control to ARDY. When SRDY is config-
ured as P106, the internal SRDY signal is driven low.
ONCE1—During reset, this pin and ONCE0 indicate to
the microcontroller the mode in which it should operate.
TMRIN0/PIO11
ONCE0 and ONCE1 are sampled on the rising edge of
Timer Input 0 (input, synchronous, edge-sensitive)
This pin supplies a clock or control signal to the internal
microcontroller timer 0. After internally synchronizing a
Low-to-High transition on TMRIN0, the microcontroller
increments the timer. TMRIN0 must be tied High if not
being used.
T TMRIN1/PIO0
Timer Input 1 (input, synchronous, edge-sensitive)
This pin supplies a clock or control signal to the internal
F ^{microcontroller timer 1. After internally synchronizing a}
Low-to-High transition on TMRIN1, the microcontroller
increments the timer. TMRIN1 must be tied High if not
being used.
TMROUT0/PIO10
A _{Timer Output 0 (output, synchronous)}
This pin supplies the system with either a single pulse
or a continuous waveform with a programmable duty
cycle.
R _TMROUT1/PIO1
Timer Output 1 (output, synchronous)
This pin supplies the system with either a single pulse
D ^{or a continuous waveform with a programmable duty}
RES. If both pins are asserted Low, the microcontroller
enters ONCE mode. Otherwise, it operates normally. In
ONCE mode, all pins assume a high-impedance state
and remain in that state until a subsequent reset oc-
curs. To guarantee the microcontroller does not inad-
vertently enter ONCE mode, ONCE1 has a weak
internal pullup resistor that is active only during a reset.
UZI/CLKSEL2/PIO26
Upper Zero Indicate (output, synchronous)
UZI—This pin lets the designer determine if an ac-
cess to the interrupt vector table is in progress by
ORing it with bits 15–10 of the address and data bus
(AD15–AD10 on the Am186ER microcontroller and
AO15–AO10 on the Am188ER microcontroller). UZI
is the logical AND of the inverted A19–A16 bits. UZI
is not held throughout the cycle. UZI is asserted in
the first period and deasserted in the second period
of a bus cycle. UZI/CLKSEL2 is three-stated during
bus holds and ONCE mode.
CLKSEL2—The clocking mode of the Am186ER and
Am188ER microcontrollers is controlled by UZI/
CLKSEL2/PIO26 and S6/CLKSEL1/PIO29 during re-
set. Both CLKSEL2 and CLKSEL1 are held High during
power-on reset because of an internal pullup resistor.
This is the default clocking mode—Times Four, which
cycle.
is used if neither clock select is asserted Low during re-
TXD/PIO27
set.
Transmit Data (output, asynchronous)
This pin supplies asynchronous serial transmit data to
the system from the internal UART of the microcontrol-
ler.
If CLKSEL2 is held Low during power-on reset, the mi-
crocontroller enters Times One mode.
This pin is latched within three crystal clock cycles after
the rising edge of RES. Refer to Reset Waveforms on
page 100 and Signals Related to Reset Waveforms on
page 100 to determine signal hold times. Note that
clock selection must be stable four clock cycles prior to
exiting reset (that is, RES going High). See Table 6 on
page 39 for specifics on the clocking modes and how to
specify them. UZI/CLKSEL2 is three-stated during bus
holds and ONCE mode.
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Am186^TMER and Am188^TMER Microcontrollers Data Sheet