AMD Am186TMER, Am188TMER Power Supply input, Write High Byte, Am186ER Microcontroller Only

If CLKSEL2 is held Low during power-on reset, the processor enters Times One mode. See Table 3-4.

This pin is latched within three crystal clock cycles after the rising edge of RES. Note that clock selection must be stable four clock cycles prior to exiting reset (i.e., RES going High).

UZI/CLKSEL2 is three-stated during bus holds and ONCE mode.

Table 3-4		Clocking Modes
				Clocking Mode
	CLKSEL2		CLKSEL1
	H		H	Times Four
	H		L	Divide by Two
	L		H	Times One
	L		L	Reserved1

Notes:

1The Reserved clocking mode should not be used. Entering the Reserved clocking mode may cause unpredictable system behavior.

VCC

Power Supply (input)

These pins supply power (+3.3 V) to the microcontroller.

Write High Byte, Am186ER Microcontroller Only

WHB

(output, three-state, synchronous)

This pin and

indicate to the system which bytes of the data bus

WLB

(upper, lower, or both) participate in a write cycle. In 80C186 designs,

this information is provided by

the least-significant address bit

BHE,

(AD0), and by

However, by using

and

the standard

WR.

WHB

WLB,

system-interface logic and external address latch that were required

are eliminated.

is asserted with AD15–AD8.

is the logical OR of

and

WHB

WHB

BHE

During reset, this pin is a pullup. This pin is three-stated during

WR.

bus holds and ONCE mode.

Write Low Byte, Am186ER Microcontroller Only

WLB/WB

(output, three-state, synchronous)

Write Byte, Am188ER Microcontroller Only

(output, three-state, synchronous)

—This pin and WHB indicate to the system which bytes of the data

WLB

bus (upper, lower, or both) participate in a write cycle. In 80C186

designs, this information is provided by

the least-significant

BHE,

address bit (AD0), and by

However, by using

and

the

WR.

WHB

WLB,

standard system interface logic and external address latch that were

required are eliminated.

is asserted with AD7–AD0.

is the logical OR of AD0 and

WLB

WLB

WR.

This pin is three-stated during bus holds and ONCE mode.

—On the Am188ER microcontroller, this pin indicates a write to the

WB

bus.

uses the same early timing as the nonmultiplexed address

WB

bus.

is associated with AD7–AD0. This pin is three-stated during

WB

bus holds and ONCE mode.

3-16 System Overview