AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 40

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

3-8
LCS/ONCE0
MCS0
MCS2–MCS1
When pulse width demodulation mode is enabled, INT4/PIO30 can be
used as a PIO.
Lower Memory Chip Select (output, synchronous, internal pullup)
ONCE Mode Request 0 (input)
LCS—This pin indicates to the system that a memory access is in
progress to the lower memory block. The base address and size of the
lower memory block are programmable up to 512 Kbytes. On the
Am186ES microcontroller, LCS is configured for 8-bit or 16-bit bus size
by the auxiliary configuration register. LCS is held High during a bus
hold condition.
ONCE0—During reset, this pin and ONCE1 indicate to the
microcontroller the mode in which it should operate. ONCE0 and
ONCE1 are sampled on the rising edge of 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 occurs. To guarantee that the
microcontroller does not inadvertently enter ONCE mode, ONCE0 has
a weak internal pullup resistor that is active only during reset. This pin
is not three-stated during a bus hold condition.
(MCS0/PIO14)
Midrange Memory Chip Select 0
(output, synchronous, internal pullup)
This pin indicates to the system that a memory access is in progress
to the corresponding region of the midrange memory block. The base
address and size of the mid-range memory block are programmable.
On the Am186ES microcontroller, MCS0 is configured for 8-bit or 16-
bit bus size by the auxiliary configuration register. MCS0 is held High
during a bus hold condition. In addition, it has weak internal pullup
resistors that are active during reset.
This signal functions like the corresponding signal in the Am186EM and
Am188EM microcontrollers except that MCS0 can be programmed as
the chip select for the entire middle chip select address range.
(MCS2/PIO24, MCS1/PIO15)
Midrange Memory Chip Selects
(output, synchronous, internal pullup)
These pins indicate to the system that a memory access is in progress
to the corresponding region of the midrange memory block. The base
address and size of the midrange memory block are programmable.
On the Am186ES microcontroller, MCS2–MCS1 are configured for 8-
bit or 16-bit bus size by the auxiliary configuration register. MCS2–
MCS1 are held High during a bus hold condition. In addition, they have
weak internal pullup resistors that are active during reset.
These signals function like the signals in the Am186EM and Am188EM
microcontrollers except that if MCS0 is programmed to be active for the
entire middle chip-select range, then these signals are available as
PIOs.
System Overview