2001 Apr 06

15

Philips Semiconductors

Preliminary specification

P87C51MB2/P87C51MC2

80C51 8-bit microcontroller family with extended memory

64KB/96KB OTP with 2KB/3KB RAM

UARTS

P87C51Mx2 includes two enhanced UART ports with one independent Baud Rate Generator:

• UART 0 is the standard 51MX enhanced UART as described in the User Manual. It can be selected to use Timer1 overflow,

Timer2 overflow or the independent Baud Rate Generator.

• UART 1 only uses the independent Baud Rate Generator to generate its baud rate. It has the same baud rate for both

transmission and reception.

• The Baud Rate Generator is described in the User Manual.

Each of the UARTs has one set of enhanced UART SFRs. Please refer to the descriptions on the corresponding SFRs in the

User Manual:

PCON.7 and PCON.6 SFR Bits

The PCON.7 and PCON.6 SFR bits configure the UARTs as follows:

• PCON.7 (SMOD1) - Baud Rate Control bit for serial port 0. When 0, the baud rate for UART 0 will be the input rate (T1 timer

or baud rate generator, as determined by the BRGCON extended SFR) divided by two. When 1, the baud rate for UART 0 will

be the input rate (T1 timer or baud rate generator). UART 1 is not affected by this bit

• PCON.6 (SMOD0) - Framing Error Location:

- When 0, bit 7 of S0CON and S1CON will function as SM0 for UARTs 0 and 1 respectively.

- When 1, bit 7 of S0CON and S1CON will be used for framing error status for UART 0 and 1 respectively.

PCON.6 also determines when the UART receive interrupts RI_0 and RI_1 occur in UART modes 2 or 3. (Refer to User

Manual for details.)

Register

Description

SFR Location

51MX Extended SFR

Location

See Description in

User Manual on

S0CON

Serial Port 0 Control

98H

SCON

S0BUF

Serial Port 0 Data Buffer

99H

SBUF

S0ADDR

Serial Port 0 Address

A9H

SADDR

S0ADEN

Serial Port 0 Address Enable

B9H

SADEN

S0STAT

Serial Port 0 Status

8CH

SSTAT

S1CON

Serial Port 1 Control

80H

SCON

S1BUF

Serial Port 1 Data Buffer

81H

SBUF

S1ADDR

Serial Port 1 Address

82H

SADDR

S1ADEN

Serial Port 1 Address Enable

83H

SADEN

S1STAT

Serial Port 1 Status

84H

SSTAT

Table 3: UARTs 0 and 1 SFRs.