AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 157

• 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

10.2.3
Figure 10-5
Serial Port 0/1 Transmit Registers
(SP0TD/SP1TD, Offset 84h/14h)
The transmit registers (Figure 10-5) are written by software with the value to be transmitted
over the serial interface. The transmitter is double-buffered; data to be transmitted is copied
from the transmit register to the transmit shift register (which is not accessible to software)
before transmitting. The state of the transmit and transmit shift registers is reflected in the
TEMT and THRE bits in the associated Serial Port Status register.
When hardware handshaking is enabled, the transmitter will not transmit data while RTS/
RTR inputs are deasserted. Data is held in the transmit and transmit shift registers without
affecting the transmit pin.
The serial port transmit register in the Am186EM and Am188EM microcontrollers is
renamed in the Am186ES and Am188ES microcontrollers as the Serial Port 0 Transmit
register.
Serial Port 0/1 Transmit Registers
The value of SPTD at reset is undefined.
Bits 15–8: Reserved
Bit 7–0: Transmit Data (TDATA)—This field contains data to be transmitted through the
asynchronous serial port.
15
Reserved
Asynchronous Serial Port
7
TDATA
0
10-11