PCA5007 datasheet(23/112 Pages) PHILIPS

23 / 112 page

1998 Oct 07

Philips Semiconductors

Product speciﬁcation

Pager baseband controller

PCA5007

6.9

Serial interface SIO0: UART

The UART interface of the PCA5007 implements a subset

of the complete standard as defined in e.g. the P80CL580.

6.9.1

DIFFERENCES TO THE STANDARD 80C51 UART

The following deviations from the standard exist:

• If [SM1 and SM0] = 10 then Mode 1 (8-bit data

transmission) is selected, with a fixed baud rate

(4800/9600 bits/s)

• If [SM1 and SM0] = 01 then Mode 2 (9-bit data

transmission) is selected, with a fixed baud rate

(4800/9600 bits/s)

• Modes 0 and 3 and the variable baud rate selection

using Timer 1 overflow is not available

• The SM2 bit has no function

• The time reference for Modes 1 and 2 is taken from the

76.8 kHz oscillator, instead of the original

6.9.2

UART MODES

This serial port is full duplex which means that it can

transmit and receive simultaneously. It is also

receive-buffered and can commence reception of a

second byte before a previously received byte has been

read from the register. However, if the first byte has not

been read by the time the reception of the second byte is

complete, the second byte will be lost. The serial port

receive and transmit registers are both accessed via the

special function register S0BUF. Writing to S0BUF loads

the transmit register and reading from S0BUF accesses a

physically separate receive register.

OSC

-----------

The serial port can operate in 2 modes:

Mode 1 10 bits are transmitted (through TXD) or received

(through RXD): a START bit (0), 8 data bits (LSB

first) and a STOP bit (1). On receive, the stop bit

goes into RB8 in special function register S0CON

(see Figs 9 and 10).

Mode 2 11 bits are transmitted (through TXD) or received

(through RXD): a START bit (0), 8 data bits (LSB

first), a programmable 9th data bit and a STOP

bit (1). On transmit, the 9th data bit (TB8 in

S0CON) can be assigned the value of 0 or 1.

Or, for example, the parity bit (P, in the PSW)

could be moved into TB8. On receive, the

9th data bit goes into RB8 in S0CON, while the

STOP bit is ignored (see Figs 9 and 11).

In both modes the baud rate can be selected to either

4800 or 9600 depending on the SMOD bit in the PCON

SFR. If SMOD = 0 the baud rate is 4800, if SMOD = 1 the

baud rate is 9600 with a 76.8 kHz quartz crystal.

In both modes, transmission is initiated by any instruction

that uses S0BUF as a destination register. Reception is

initiated by the incoming start bit if REN = 1.

6.9.3

SERIAL PORT CONTROL REGISTER (S0CON)

The serial port control and status register is the special

function register S0CON (see Table 16). The register

contains not only the mode selection bits, but also the

9th data bit for transmit and receive (TB8 and RB8), and

the serial port interrupt bits (TI and RI).

Table 16 Serial Port Control Register (S0CON, SFR address 98H)

76543210

SM0

SM1

−

REN

TB8

RB8

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