PCA5007 Datasheet, PDF (23/112 Pages) NXP Semiconductors – Pager baseband controller

Philips Semiconductors
Pager baseband controller
Product specification
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 -f-^O-1---^S_2---^C--
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.
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)
7
6
5
4
3
2
1
0
SM0
SM1
−
REN
TB8
RB8
TI
RI
1998 Oct 07
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