NS32FX100-15 Datasheet, PDF (38/94 Pages) National Semiconductor (TI) – System Controller

2 0 Architecture (Continued)
7
6
5
4
3
2
1
0
TBRK res
res
res
TSB EDB PEN EPS
EPS
PEN
EDB
TSB
TBRK
UCLST
Even Parity Select
0 Odd parity
1 Even parity
Even parity means that the total number of bits
set (including the parity bit) is even
Parity Enable
0 Parity disabled
1 Parity enabled
Number of data bits
0 Seven data bits
1 Eight data bits
Number of stop bits transmitted
0 One stop bit
1 Two stop bits
Transmission Break Control implemented by
forcing UTXD pin low
0 No break signal
1 Break signal
Undefined results when TBRK is ‘‘1’’ while
UCLST TE is ‘‘0’’
UART Clearing Status register 8-bit register
7
6
5
4
3
2
1
0
TR
TE
res
OE
res
FE
PE
RF
Receive status bits Upon reset these status bits are
cleared to ‘‘0’’
RF Receive Full RF e 1 when URXB is loaded by the
shift register
PE Parity Error PE e 1 when parity error is detected
FE Frame Error FE e 1 when the first stop bit is ‘‘0’’
OE Overrun Error OE e 1 when both reception buffer and
shifter are full and a new character is received
Transmit status bits Upon reset these status bits are set to
‘‘1’’
TE Transmit Empty TE e 1 when both UTXB and the
shifter are empty
TR Transmit Ready TR e 1 when UTXB is empty
OE status bit is sticky Once set it is cleared by reset or by
writing into UCLST (data written into this register is ignored)
RF is cleared during reset It is set to ‘‘1’’ when URXB is
loaded by the shift register It is updated by a URXB read
RF remains ‘‘1’’ if the shifter already holds a new character
and is cleared to ‘‘0’’ if the shifter did not finish reception of
a new character
PE and FE bits are sticky These two bits are cleared during
reset and whenever UCLST is read
2 7 4 Usage Recommendations
1 Before activating the UART program the appropriate
Ports module registers PADI PAMS PBDO PBMS
PCDO PCMS and PCEN to connect the UART module
to the NS32FX100 I O pins
2 Initialization
a Disable interrupts or mask the UART interrupt
b Initialize UBRG and then UCNTL
c Clear receiver status bits using URXB and UCLST
d Enable UART interrupt if required
e Program the PAMS register in the Ports module as
follows
MS0 must be cleared before data is trans-
mitted from the UART
MS1 must be set before data can be re-
ceived on the URXT pin
3 To use the PE and FE status bits as non-sticky bits read
the UCLST before reading URXB Note that right after
URXB is read it might be loaded with a new character
which was waiting in the shifter and those status bits
might be set by the new URXB Therefore it is recom-
mended to read UCLST first and then read URXB thus
keeping coherence between the contents of URXB and
UCLST
4 When UTEN is inactive the TE bit does not ensure that
two characters may be written to the UTXB The TR bit
must be ‘‘0’’ before each UTXB write
2 8 MICROWIRE (MWIRE)
2 8 1 Features
Y _{Operates as a MICROWIRE master}
Y _{Programmable shift-clock frequency}
Y _{8-bit serial I O data shift register}
Y _{Busy flag for polling and as an interrupt source}
Y _{Two modes of clocking data}
2 8 2 Operation
The MICROWIRE (MWIRE) is a serial synchronous commu-
nication interface It enables an interface with any National
Semiconductor chip that supports MICROWIRE protocol
such as COPs and EEPROMs The MWIRE interface con-
sists of three signals serial data in serial data out and
serial clock Several devices may share the same MWIRE
channel by means of device-select signals Such select sig-
nals may be provided by the Ports module The MWIRE
outputs may be TRI-STATED by the Ports module A high
level interrupt is generated when the MWIRE is not busy
and is cleared only while MWIRE is busy The serial data is
sampled on the serial clock falling edge The serial data out
may change on the serial clock rising or falling edge ac-
cording to the software selected mode
2 8 3 Registers
MWSIO MICROWIRE Serial I O Shift register 8-bit shift
register
Used for data transfer over the MWIRE channel
Bit-7 the most significant bit is transmitted first
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