IA186ER/IA188ER
Data Sheet
16-Bit/8-Bit Microcontrollers with RAM
February 25, 2013
2.2.47 whb_n (IA186ER)—Write High Byte (synchronous output with tristate)
The whb_n and wlb_n pins indicate to the system 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.
2.2.48 wlb_n/wb_n—Write Low Byte (IA186ER) (synchronous output with tristate)/Write
Byte (IA188ER) (synchronous output with tristate)
The wlb_n and whb_n pins indicate to the system 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 IA188ER 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.
2.2.49 wr_n—Write Strobe (synchronous output)
The wr_n pin indicates 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.
2.2.50 x1—Crystal Input (input)
The x1 and x2 pins are the connections for a fundamental-mode, parallel-resonant crystal used
by the internal oscillator circuit. An external clock source for the microcontroller is connected to
x1. The x2 pin is left unconnected.
2.2.51 x2—Crystal Input (input)
The x1 and x2 pins are the connections for a fundamental-mode, parallel-resonant crystal used
by the internal oscillator circuit. An external clock source for the microcontroller is connected to
x1. The x2 pin is left unconnected.
2.3
Pins Used by Emulators
The following pins are used by emulators:
a19–a0
ao15–ao8 (on the IA188ER)
ad7–ad0
ale
bhe_n/aden_n (on the IA186ER)
clkouta
rfsh2_n/aden_n (on the IA188ER)
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