AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 148

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

Table 10-1
10.1.1.1
Figure 10-1
10.1.1.2
10-2
Serial Port External Pins
Each port is provided with two data pins (RXD0/RXD1 and TXD0/TXD1) and two flow control
signals (RTS0, RTS1/RTR0, RTR1). The flow control signals are configurable by software
to support several different protocols. These protocols are discussed below. Hardware flow
control is enabled for the serial port when the FC bit in the serial port control register is set.
DCE/DTE Protocol
The Am186ES and Am188ES microcontrollers implement only a subset of the data
communication equipment/data terminal equipment (DCE/DTE) protocol. The DCE/DTE
protocol provides flow control where one serial port is receiving data and the other serial
port is sending data, as shown in 10.1.1.2.
DCE/DTE Protocol
DCE/DTE Protocol
The Am186ES and Am188ES microcontrollers’ serial ports can function as either DTE or
DCE devices. To implement the DCE device, the ENRX bit should be set and the RTS bit
should be cleared for the associated serial port. To implement the DTE device, the ENRX
bit should be cleared and the RTS bit should be set for the associated serial port. These
bits are located in the AUXCON register.
In the DCE/DTE protocol, the DTE device sends data. When data is available to send, the
DTE device asserts the RTS signal. The RTS signal is interpreted by the DCE device as a
request to enable its receiver. The DCE device signals the DTE device that it is ready to
receive data by asserting the RTR signal. The interface is asymmetrical since the DTE
device cannot signal the DCE device that it is ready to receive data; neither can the DCE
device signal that it is ready to send data.
Pin
Designation
RXD0, RXD1
TXD0, TXD1
CTS0, CTS1/
ENRX0, ENRX1
RTS0, RTS1/
RTR0, RTR1
RTS = Request to send output from transmitter
RTR = Ready to receive output from receiver
CTS = Clear to send input to transmitter
ENRX = Enable receiver request input to receiver
Asynchronous Serial Port
DCE
ENRX
Pin Function
Receives serial port data
Transmits serial port data
Clear to send or enable receiver
request
Ready to send or ready to receive
RTR
RTS
CTS
DTE