
Chapter 14. Timers/Counters and Serial Interface Page 14-13
The registers associated with the serial ports are as follows. (Registers PCON and EICON also
include some functionality which is not part of the Serial Interface).
• PCON (SFR 0x87) — Bit 7, Serial Port 0 rate control SMOD0 (Table 14-13).
• SCON0 (SFR 0x98) — Serial Port 0 control (Table 14-11).
• SBUF0 (SFR 0x99) — Serial Port 0 transmit/receive buffer.
• EICON (SFR 0xD8) — Bit 7, Serial Port 1 rate control SMOD1 (Table 14-12).
• SCON1 (SFR 0xC0) — Serial Port 1 control (Table 14-14).
• SBUF1 (SFR 0xC1) — Serial Port 1 transmit/receive buffer.
• T2CON (SFR 0xC8) — Baud clock source for modes 1 and 3 (RCLK and TCLK in
Table 14-5).
• UART230 (0xE608) — High-Speed Baud Rate Generator enable (see Section 14.3.2,
"High-Speed Baud Rate Generator").
14.3.1 803x/805x Compatibility
The implementation of the serial interface is similar to that of the Dallas Semiconductor,
DS80C320. Table 14-8 summarizes the differences in serial interface implementation between the
Intel 8051, the Dallas Semiconductor DS80C320, and the FX2.
Table 14-7. Serial Port Modes
Mode
Sync /
Async
Baud-Clock Source
Data
Bits
Start /
Stop
9th Bit
Function
0 Sync CLKOUT/4 or CLKOUT/12 8 None None
1 Async Timer 1 (Ports 0 and 1),
Timer 2 (Port 0 only), or
High-Speed Baud Rate Generator (Ports 0 and 1)
8 1 start, 1 stop None
2 Async CLKOUT/32 or CLKOUT/64 9 1 start, 1 stop 0, 1, or parity
3 Async Timer 1 (Ports 0 and 1),
Timer 2 (Port 0 only), or
High-Speed Baud Rate Generator (Ports 0 and 1)
9 1 start, 1 stop 0, 1, or parity
Note: The High-Speed Baud Rate Generator provides 115.2K or 230.4K baud rates (see Section 14.3.2
).
Table 14-8. Serial Interface Implementation Comparison
Feature Intel 8051 Dallas DS80C320 FX2
Number of serial ports 1 2 2
Framing error detection not implemented implemented not implemented
Slave address comparison for
multiprocessor communication
not implemented implemented not implemented
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