HPC46100 Datasheet, PDF (22/32 Pages) National Semiconductor (TI) – HPC46100 High-Performance microController with DSP Capability

Timer Overview (Continued)
the timer and operation will continue as in the PWM mode
Alternately an interrupt from the RnB load can be used to
branch to a routine that would set the timer into mode 3
waiting for the trigger for another pulse Figure 25 shows a
block diagram of the timer in this mode
When the HPC46100 is a master the DIVBY register pro-
grams the frequency of the SK clock The DIVBY register
allows the SK clock frequency to be programmed in 15 se-
lectable steps from 64 Hz to 1 MHz with CKI at 16 0 MHz
The contents of the SIO register may be accessed through
any of the memory access instructions Data waiting to be
transmitted in the SIO register is clocked out on the falling
edge of the SK clock Serial data on the SI pin is clocked in
on the rising edge of the SK clock
TL DD 11289–27
FIGURE 25 Port Output Externally Triggered PWM
WATCHDOG LOGIC
The WATCHDOG Logic monitors the operations taking
place and signals upon the occurrence of any illegal activity
The illegal conditions that trigger the WATCHDOG logic are
potentially infinite loops Should the WATCHDOG register
not be written to before Timer T0 overflows twice or more
often than once every 4096 counts an infinite loop condi-
tion is assumed to have occurred Any illegal condition
forces the WATCHDOG Output (WO) pin low The WO pin is
an open drain output and can be connected to the RESET
or NMI inputs or to the users external logic
MICROWIRE PLUS
MICROWIRE PLUS is used for synchronous serial data
communications and has an 8-bit parallel-loaded serial shift
register using SI as the input and SO as the output SK is
the clock for the serial shift register (SIO) The SK clock
signal can be provided by an internal or external source
The internal clock rate is programmable by the DIVBY regis-
ter A DONE flag indicates when the data shift is completed
The MICROWIRE PLUS capability enables it to interface
with any of National Semiconductor’s MICROWIRE periph-
erals (i e A D converters display drivers EEPROMs)
MICROWIRE PLUS OPERATION
The HPC46100 can enter the MICROWIRE PLUS mode as
the master or a slave A control bit in the IRCD register
determines whether the HPC46100 is the master or slave
The shift clock is generated when the HPC46100 is config-
ured as a master An externally generated shift clock on the
SK pin is used when the HPC46100 is configured as a slave
TL DD 11289 – 28
FIGURE 26 MICROWIRE PLUS
HPC46100 UART
The HPC46100 contains a software programmable UART
The UART (see Figure 27 ) consists of a transmit shift regis-
ter a receiver shift register and five addressable registers
as follows a transmit buffer register (TBUF) a receiver buff-
er register (RBUF) a UART control and status register
(ENU) a UART receive control and status register (ENUR)
and a UART interrupt and clock source register (ENUI) The
ENU register contains flags for transmit and receive func-
tions this register also determines the length of the data
frame (7 8 or 9 bits) and the value of the ninth bit in trans-
mission The ENUR register flags framing parity and data
overrun errors while the UART is receiving Other functions
of the ENUR register include saving the ninth bit received in
the data frame reporting receiving and transmitting status
and enabling or disabling the UART’s Attention Mode of
operation
The determination of an internal or external clock source is
done by the ENUI register as well as selecting the number
of stop bits ( 1 1 or 2 stop bits) selecting between the
synchronous or asynchronous mode and enabling or dis-
abling transmit and receive interrupts The clock inputs to
the Transmitter and Receiver sections of the UART can be
individually selected to come from either an off-chip source
on the CKX pin or one of the two on-chip sources The
Divide-By (DIVBY) Register provides upward compatibility
from earlier HPC family members and the most flexible and
accurate on-chip clocking is provided by the Baud Rate
Generator (BRG)
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