Intel 386 User Manual
Page 532
A-3
SIGNAL DESCRIPTIONS
CTS1#
CTS0#
I
Clear to Send:
Indicates that the modem or data set is ready to exchange
data with the SIO channel.
EOP#
P2.7
D15:0
I/O
Data Bus:
Inputs data during memory read, I/O read, and interrupt
acknowledge cycles; outputs data during memory write and
I/O write cycles. During reads, data is latched during the
falling edge of phase 2 of T2, T2P, or T2i. During writes, this
bus is driven during phase 2 of T1 and remains active until
phase 2 of the next T1, T1P, or Ti.
—
DACK1#
DACK0#
O
DMA Channel Acknowledge:
Indicates that the DMA channel is ready to service the
requesting device. An external device uses the DRQ
n pin to
request DMA service; the DMA uses the DACK
n pin to
indicate that the request is being serviced.
TXD1
CS5#
D/C#
O
Data/Control:
Indicates whether the current bus cycle is a data cycle
(memory or I/O read or write) or a control cycle (interrupt
acknowledge, halt/shutdown, or code fetch).
—
DCD1#
DCD0#
I
Data Carrier Detect:
Indicates that the modem or data set has detected the SIO
channel’s data carrier.
DRQ0
P1.0
DRQ1
DRQ0
I
DMA External Request:
Indicates that an external device requires DMA service.
RXD1
DCD1#
DSR1#
DSR0#
I
Data Set Ready:
Indicates that the modem or data set is ready to establish
the communications link with the SIO channel.
STXCLK
P1.3
DTR1#
DTR0#
O
Data Terminal Ready:
Indicates that the SIO channel is ready to establish a
communications link with the modem or data set.
SRXCLK
P1.2
EOP#
I/OD
End-of-process:
As an input, this signal terminates a DMA transfer. As an
ouput, it indicates that a DMA transfer has completed.
CTS1#
ERROR#
I
Error:
Indicates the the math coprocessor has an error condition.
TMROUT2
FLT#
I
Float:
Forces all bidirectional and output signals except TDO to a
high-impedance state.
—
HLDA
O
Hold Acknowledge:
Indicates that the processor has relinquished local bus
control to another bus master in response to a HOLD
request.
P1.7
Table A-2. Description of Signals Available at the Device Pins (Sheet 2 of 6)
Signal
Type
Name and Description
Multiplexed With
(Alternate
Function)