
80C186EC188EC 80L186EC188EC
Table 2 Pin Descriptions
(Continued)
Pin Name
Pin
Input
Output
Pin Description
Type
States
A18S5
IO
A(L)
H(Z)
These pins drive address information during the address
phase of the bus cycle During T2 and T3 these pins drive
A17S4
R(WH)
status information (which is always 0 on the 80C186EC)
A16S3
I(0)
These pins are used as inputs during factory test driving
(A158)
P(0)
these pins low during reset will cause unspecified operation
On the 80C188EC A158 provide valid address information
for the entire bus cycle
AD15CAS2
IO
S(L)
H(Z)
These pins are part of the multiplexed ADDRESS and DATA
bus During the address phase of the bus cycle address bits
AD14CAS1
R(Z)
15 through 13 are presented on these pins and can be
AD13CAS0
I(0)
latched using ALE Data information is transferred during the
P(0)
data phase of the bus cycle Pins AD1513CAS20 drive the
82C59 slave address information during interrupt
acknowledge cycles
AD120
IO
S(L)
H(Z)
These pins provide a multiplexed ADDRESS and DATA bus
During the address phase of the bus cycle address bits 0
(AD70)
R(Z)
through 12 (0 through 7 on the 80C188EC) are presented on
I(0)
the bus and can be latched using ALE Data information is
P(0)
transferred during the data phase of the bus cycle
S20
O
H(Z)
Bus cycle Status are encoded on these pins to provide bus
transaction information S20 are encoded as follows
R(1)
I(1)
P(1)
S2
S1
S0
Bus Cycle Initiated
0
Interrupt Acknowledge
0
1
Read IO
0
1
0
Write IO
0
1
Processor HALT
1
0
Instruction Queue Fetch
1
0
1
Read Memory
1
0
Write Memory
1
Passive (No bus activity)
ALE
O
H(0)
Address Latch Enable
output is used to strobe address
information into a transparent type latch during the address
R(0)
phase of the bus cycle
I(0)
P(0)
BHE
O
H(Z)
Byte High Enable
output to indicate that the bus cycle in
progress is transferring data over the upper half of the data
(RFSH)
R(Z)
bus BHE and A0 have the following logical encoding
I(1)
P(1)
A0
BHE
Encoding
(for 80C186EC
80L186EC only)
0
Word transfer
0
1
Even Byte transfer
1
0
Odd Byte transfer
1
Refresh operation
On the 80C188EC80L188EC RFSH is asserted low to
indicate a refresh bus cycle
NOTE
Pin names in parentheses apply to the 80C188EC80L188EC
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