8XC196KC/8XC196KC20
PIN DESCRIPTIONS
Symbol
V
CC
V
SS
V
REF
ANGND
V
PP
XTAL1
XTAL2
CLKOUT
RESET
BUSWIDTH
NMI
INST
EA
Name and Function
Main supply voltage (5V).
Digital circuit ground (0V). There are multiple V
SS
pins, all of which must be connected.
Reference voltage for the A/D converter (5V). V
REF
is also the supply voltage to the analog
portion of the A/D converter and the logic used to read Port 0. Must be connected for A/D
and Port 0 to function.
Reference ground for the A/D converter. Must be held at nominally the same potential as
V
SS
.
Timing pin for the return from powerdown circuit. This pin also supplies the programming
voltage on the EPROM device.
Input of the oscillator inverter and of the internal clock generator.
Output of the oscillator inverter.
Output of the internal clock generator. The frequency of CLKOUT is
frequency.
the oscillator
Reset input and open drain output.
Input for buswidth selection. If CCR bit 1 is a one, this pin selects the bus width for the bus
cycle in progress. If BUSWIDTH is a 1, a 16-bit bus cycle occurs. If BUSWIDTH is a 0 an
8-bit cycle occurs. If CCR bit 1 is a 0, the bus is always an 8-bit bus.
A positive transition causes a vector through 203EH.
Output high during an external memory read indicates the read is an instruction fetch. INST
is valid throughout the bus cycle. INST is activated only during external memory accesses
and output low for a data fetch.
Input for memory select (External Access). EA equal high causes memory accesses to
locations 2000H through 5FFFH to be directed to on-chip ROM/E PROM. EA equal to low
causes accesses to those locations to be directed to off-chip memory. Also used to enter
programming mode.
Address Latch Enable or Address Valid output, as selected by CCR. Both pin options
provide a signal to demultiplex the address from the address/data bus. When the pin is
ADV, it goes inactive high at the end of the bus cycle. ALE/ADV is activated only during
external memory accesses.
Read signal output to external memory. RD is activated only during external memory reads.
Write and Write Low output to external memory, as selected by the CCR. WR will go low for
every external write, while WRL will go low only for external writes where an even byte is
being written. WR/WRL is activated only during external memory writes.
Bus High Enable or Write High output to external memory, as selected by the CCR. BHE will
go low for external writes to the high byte of the data bus. WRH will go low for external
writes where an odd byte is being written. BHE/WRH is activated only during external
memory writes.
Ready input to lengthen external memory cycles, for interfacing to slow or dynamic memory,
or for bus sharing. When the external memory is not being used, READY has no effect.
Inputs to High Speed Input Unit. Four HSI pins are available: HSI.0, HSI.1, HSI.2 and HSI.3.
Two of them (HSI.2 and HSI.3) are shared with the HSO Unit.
Outputs from High Speed Output Unit. Six HSO pins are available: HSO.0, HSO.1, HSO.2,
HSI.3, HSO.4 and HSO.5. Two of them (HSO.4 and HSO.5) are shared with the HSI Unit.
8-bit high impedance input-only port. These pins can be used as digital inputs and/or as
analog inputs to the on-chip A/D converter.
8-bit quasi-bidirectional I/O port.
8-bit multi-functional port. All of its pins are shared with other functions in the 80C196KC.
Pins 2.6 and 2.7 are quasi-bidirectional.
ALE/ADV
RD
WR/WRL
BHE/WRH
READY
HSI
HSO
Port 0
Port 1
Port 2
7
ROCHESTER [ Rochester Electronics ]
