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80C186EC/188EC, 80L186EC/188EC
Table 2. Pin Descriptions
(Continued)
Pin Name
Pin
Input
Output
Pin Description
Type
Type
States
PEREQ
I
A(L)
Ð
Processor Extension REQuest
signals that a data
transfer between an 80C187 Numerics Processor
Extension and Memory is pending. Systems not using an
80C187 must tie this pin to V
SS
. This signal does not exist
on the 80C188EC/80L188EC.
UCS
O
Ð
H(1)
Upper Chip Select
will go active whenever the address of
a memory or I/O bus cycle is within the address range
R(1)
programmed by the user. After reset, UCS is configured to
I(1)
be active for memory accesses between 0FFC00H and
P(1)
0FFFFFH.
LCS
O
Ð
H(1)
Lower Chip Select
will go active whenever the address of
a memory or I/O bus cycle is within the address range
R(1)
programmed by the user. LCS is inactive after a reset.
I(1)
P(1)
P1.0/GCS0
O
Ð
H(X)/H(1)
These pins provide a multiplexed function. If enabled,
each pin can provide a
General purpose Chip Select
P1.1/GCS1
R(1)
output which will go active whenever the address of a
P1.2/GCS2
I(X)/I(1)
memory or I/O bus cycle is within the address limitations
P1.3/GCS3
P(X)/P(1)
programmed by the user. When not programmed as a
P1.4/GCS4
Chip-Select, each pin may be used as a general purpose
P1.5/GCS5
output port.
P1.6/GCS6
P1.7/GCS7
T0OUT
O
Ð
H(Q)
Timer OUTput
pins can be programmed to provide single
clock or continuous waveform generation, depending on
T1OUT
R(1)
the timer mode selected.
I(Q)
P(X)
T0IN
I
A(L)
Ð
Timer INput
is used either as clock or control signals,
depending on the timer mode selected. This pin may be
T1IN
A(E)
either level or edge sensitive depending on the
programming mode.
INT7:0
I
A(L)
Ð
Maskable INTerrupt
input will cause a vector to a specific
Type interrupt routine. The INT6:0 pins can be used as
A(E)
cascade inputs from slave 8259A devices. The INT pins
can be configured as level or edge sensitive.
INTA
O
Ð
H(1)
INTerrupt Acknowledge
output is a handshaking signal
used by external 82C59A Programmable Interrupt
R(1)
Controllers.
I(1)
P(1)
P3.5
I/O
A(L)
H(X)
Bidirectional, open-drain port pins.
P3.4
R(Z)
I(X)
H(X)
P3.3/DMAI1
O
Ð
H(X)
DMA Interrupt
output goes active to indicate that the
channel has completed a transfer. DMAI1 and DMAI0 are
P3.2/DMAI0
R(0)
multiplexed with output only port functions.
I(Q)
P(X)
NOTE:
Pin names in parentheses apply to the 80C188EC/80L188EC.
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