Controlling and Resetting the Port
10-10
10.3.2 I/O Status Register (IOSR)
The IOSR returns the status of the asynchronous serial port and of I/O pins
IO0–IO3. The IOSR is a 16-bit, on-chip register mapped to address FFF6h in
I/O space. Figure 10–4 shows the fields in the IOSR, and bit descriptions fol-
low the figure.
Figure 10–4. I/O Status Register (IOSR) — I/O-Space Address FFF6h
Á
Á
ÁÁÁÁÁ
ÁÁÁÁÁ
15
ÁÁÁÁ
ÁÁÁÁ
14
ÁÁÁÁÁ
ÁÁÁÁÁ
13
ÁÁÁÁÁ
ÁÁÁÁÁ
12
ÁÁÁÁ
ÁÁÁÁ
11
ÁÁÁÁÁ
ÁÁÁÁÁ
10
ÁÁÁÁ
ÁÁÁÁ
9
ÁÁÁÁÁ
ÁÁÁÁÁ
8
Á
Á
Á
Á
ÉÉÉÉÉ
ÉÉÉÉÉ
Reserved
ÁÁÁÁ
ÁÁÁÁ
ADC
ÁÁÁÁÁ
ÁÁÁÁÁ
BI
ÁÁÁÁÁ
ÁÁÁÁÁ
TEMT
ÁÁÁÁ
ÁÁÁÁ
THRE
ÁÁÁÁÁ
ÁÁÁÁÁ
FE
ÁÁÁÁ
ÁÁÁÁ
OE
ÁÁÁÁÁ
ÁÁÁÁÁ
DR
Á
Á
Á
Á
ÁÁÁÁÁ
ÁÁÁÁÁ
0
ÁÁÁÁ
ÁÁÁÁ
R/W1C–0
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W1C–0
ÁÁÁÁÁ
ÁÁÁÁÁ
R–1
ÁÁÁÁ
ÁÁÁÁ
R–1
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W1C–0
ÁÁÁÁ
ÁÁÁÁ
R/W1C–0
ÁÁÁÁÁ
ÁÁÁÁÁ
R–0
Á
Á
Á
Á
ÁÁÁÁÁ
ÁÁÁÁÁ
7
ÁÁÁÁ
ÁÁÁÁ
6
ÁÁÁÁÁ
ÁÁÁÁÁ
5
ÁÁÁÁÁ
ÁÁÁÁÁ
4
ÁÁÁÁ
ÁÁÁÁ
3
ÁÁÁÁÁ
ÁÁÁÁÁ
2
ÁÁÁÁ
ÁÁÁÁ
1
ÁÁÁÁÁ
ÁÁÁÁÁ
0
Á
Á
Á
Á
ÁÁÁÁÁ
ÁÁÁÁÁ
DIO3
ÁÁÁÁ
ÁÁÁÁ
DIO2
ÁÁÁÁÁ
ÁÁÁÁÁ
DIO1
ÁÁÁÁÁ
ÁÁÁÁÁ
DIO0
ÁÁÁÁ
ÁÁÁÁ
IO3
ÁÁÁÁÁ
ÁÁÁÁÁ
IO2
ÁÁÁÁ
ÁÁÁÁ
IO1
ÁÁÁÁÁ
ÁÁÁÁÁ
IO0
Á
Á
Á
Á
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W1C–x
ÁÁÁÁ
ÁÁÁÁ
R/W1C–x
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W1C–x
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W1C–x
ÁÁÁÁ
ÁÁÁÁ
R/W†–x
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W†–x
ÁÁÁÁ
ÁÁÁÁ
R/W†–x
ÁÁÁÁÁ
ÁÁÁÁÁ
R/W†–x
Á
Á
Á
Á
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ
Note:
0 = Always read as 0; R=Read access; W1C=Write 1 to this bit to clear it to 0; W = Write access;
value following dash (–) is value after reset (x means value not affected by reset).
† This bit can be written to only when it is configured as an output by the corresponding CIO bit in the ASPCR.
Á
Á
Á
Bit 15
Reserved. Always read as 0.
Bit 14
ADC —
A detect complete bit. If the CAD bit of the ASPCR is 1 and the
character
A or a is received in the ADTR, ADC is set to 1. The character A
or
a remains in the ADTR after it has been detected. To avoid an overrun er-
ror when the next character arrives, the ADTR should be read immediately
after ADC is set.
ADC = 0
A or a not has not been detected. No receive interrupt
(TXRXINT) will be generated.
ADC = 1
A or a has been detected. If the CAD bit of the ASPCR is also
1, a receive interrupt (TXRXINT) will be generated, regardless
of the values of the DIM, TIM, and RIM bits of the ASPCR. For
as long as ADC = 1 and CAD = 1, a receive interrupt will occur.
Bit 13
BI — Break interrupt indicator. BI = 1 indicates that a break has been de-
tected on the RX pin. Write a 1 to this bit to clear it to 0. BI is also cleared to
0 at reset.
A break on the RX pin also generates an interrupt (TXRXINT).
Bit 12
TEMT — Transmit empty indicator. TEMT = 1 indicates whether the trans-
mit register (ADTR) and/or transmit shift register (AXSR) are full or empty.
This bit is set to 1 on reset.
TEMT = 0
The ADTR and/or AXSR are full.
TEMT = 1
The ADTR and the AXSR are empty; the ADTR is ready for a
new character to transmit.