IA186ES/IA188ES
Data Sheet
8-Bit/16-Bit Microcontrollers
November 15, 2011
2.2.49 uzi_n/pio26—Upper Zero Indicate (synchronous output)
This pin allows the designer to determine if an access 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 AI186 and ao15–
ao10 on the IA188ES). The uzi_n is the logical AND of the inverted a19–a16 bits. It asserts in
the first period of a bus cycle and is held throughout the cycle.
2.2.50 vcc—Power Supply (input)
These pins supply power (+5V +10%) to the microcontroller.
2.2.51 whb_n (IA186ES only)—Write High Byte (synchronous output with tristate)
This pin and wlb_n provide an indication to the system of which bytes of the data bus (upper,
lower, or both) are taking part in a write cycle. The whb_n is asserted with ad15–ad8 and is the
logical OR of bhe_n and wr_n. It is tristated during reset.
2.2.52 wlb_n/wb_n—Write Low Byte (IA186ES only) (synchronous output with
tristate)/Write Byte (IA188ES only) (synchronous output with tristate)
The wlb_n and whb_n provide an indication to the system of which bytes of the data bus (upper,
lower, or both) are taking part in a write cycle. The wlb_n is asserted with ad7–ad0 and is the
logical OR of ad0 and wr_n. It is tristated during reset.
On the IA188ES microcontroller, wb_n provides an indication that a write to the bus is
occurring. It shares the same early timing as that of the non-multiplexed address bus, and is
associated with ad7–ad0. It is tristated during reset.
2.2.53 wr_n—Write Strobe (synchronous output)
This pin provides an indication to the system that the data currently on the bus is to be written to
a memory or I/O device. It is tristated during a bus hold or reset.
2.2.54 x1—Crystal Input
This pin and x2 are the connections for a fundamental mode or third-overtone, parallel-resonant
crystal used by the internal oscillator circuit. An external clock source for the microcontroller is
connected to x1 while the x2 pin is left unconnected.
2.2.55 x2—Crystal Input
This pin and x1 are the connections for a fundamental mode or third-overtone, parallel-resonant
crystal used by the internal oscillator circuit. An external clock source for the microcontroller is
connected to x1 while the x2 pin is left unconnected.
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