
Asynchronous Serial Port
10-12
10.2.4
Serial Port 0/1 Receive Registers
(SP0RD/SP1RD, Offset 86h/16h)
These registers (Figure 10-6) contain data received over the serial port. The receiver is
double-buffered; the receive section can be receiving a subsequent frame of data in the
receive shift register (which is not accessible to software) while the receive data register is
being read.
The Receive-Data-Ready (RDR) bit in the serial port status register reports the current
state of this register. When the RDR bit is set, the receive register contains valid unread
data. The RDR bit is automatically cleared when the receive register is read.
When hardware handshaking is enabled, the CTS/ENRX signals are deasserted while the
receive register contains valid unread data. Reading the receive register causes the CTS/
ENRX signals to be asserted. This behavior prevents overrun errors, but may result in
delays between character transmissions.
Figure 10-6
Serial Port Receive 0/1 Registers
The value of SPRD at reset is undefined.
Bits 15–8: Reserved
Bits 7–0: Receive Data (RDATA)—This field holds valid data received over the serial line
only when the RDR bit in the associated serial port control register is set.
15
7
0
Reserved
RDATA
Содержание Am186 ES
Страница 1: ...Am186 ES and Am188 ES User s Manual...
Страница 4: ...iv...
Страница 12: ...Table of Contents xii...
Страница 22: ...Features and Performance 1 8...
Страница 60: ...System Overview 3 28...
Страница 84: ...Chip Select Unit 5 14...
Страница 132: ...Timer Control Unit 8 8...
Страница 166: ...Programmable I O Pins 11 6...
Страница 184: ...Register Summary A 18...