IA186EM_04 Datasheet, PDF (69/133 Pages) InnovASIC, Inc – 8/16-Bit Microcontrollers

IA186EM/IA188EM
8/16-BIT Microcontrollers
Data Sheet
As of Production Version -03
After power-on-reset, ucs_n is active low and program execution begins at FFFF0h with the default
configuration of the ucs_n chip select is for 64 Kbytes memory range from F0000h to FFFFFh.
once1_n – (ONCE – ON Circuit Emulation). This pin and its companion pin once0_n define the
microcontroller mode during reset. These two pins are sampled on the rising edge of res_n and if both
are asserted low the microcontroller starts in ONCE mode, else it starts normally. In ONCE mode all pins
are tristated and remain so until a subsequent reset. To prevent the microcontroller from entering ONCE
mode inadvertently, this pin has a weak pull-up that is only present during reset. Finally, this pin is not
tristated during bus hold.
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 AI186EM and ao15-ao10 on the
AI188EM). uzi_n is the logical OR of the inverted a19-a16 bits. It asserts in the first period of a bus
cycle and is held throughout the cycle.
At reset uzi_n should be pulled high or should be allowed to float. If this pin is pulled low at reset, the
microcontroller enters a reserved clock test mode.
v_cc – Power Supply (input)
These pins supply power (+5V) to the microcontroller.
whb_n – Write High Byte - IA186EM only - (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. whb_n is asserted with ad15_ad8 and is the logical OR of bhe_n
and wr_n. It is tristated during reset.
wlb_n/wb_n – Write Low Byte - IA186EM only - (synchronous output with tristate) / Write Byte –
IA188EM only - (synchronous output with tristate)
wlb_n - 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. wlb_n is asserted with ad7_ad0 and is the logical OR of
ad0 and wr_n. It is tristated during reset.
wb_n – On the IA188EM 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.
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.
x1 – Crystal Input (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.
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