CP3BT10 Datasheet, PDF (124/210 Pages) National Semiconductor (TI) – Reprogrammable Connectivity Processor with Bluetooth and USB Interfaces

20.0 Microwire/SPI Interface
Microwire/Plus is a synchronous serial communications
protocol, originally implemented in National Semiconduc-
tor's COP8^® and HPC families of microcontrollers to mini-
mize the number of connections, and therefore the cost, of
communicating with peripherals.
The CP3BT10 has an enhanced Microwire/SPI interface
module (MWSPI) that can communicate with all peripherals
that conform to Microwire or Serial Peripheral Interface
(SPI) specifications. This enhanced Microwire interface is
capable of operating as either a master or slave and in 8- or
16-bit mode. Figure 47 shows a typical enhanced Microwire
interface application.
GPIO
MWCS
I/O
Lines
Master
CS
8-Bit
A/D
DO SK DI
CS
1K Bit
EEPROM
DO SK DI
CS
LCD
Display
Driver
SK DI
CS
VF
Display
Driver
SK DI
Slave
I/O
Lines
MDIDO
MDODI
MSK
MDIDO
MDODI
MSK
DS067
Figure 47. Microwire Interface
The enhanced Microwire interface module includes the fol-
lowing features:
„ Programmable operation as a Master or Slave
„ Programmable shift-clock frequency (master only)
„ Programmable 8- or 16-bit mode of operation
„ 8- or 16-bit serial I/O data shift register
„ Two modes of clocking data
„ Serial clock can be low or high when idle
„ 16-bit read buffer
„ Busy bit, Read Buffer Full bit, and Overrun bit for polling
and as interrupt sources
„ Supports multiple masters
„ Maximum bit rate of 10M bits/second (master mode) 5M
bits/second (slave mode) at 20 MHz System Clock
„ Supports very low-end slaves with the Slave Ready out-
put
„ Echo back enable/disable (Slave only)
The three-wire system includes: the serial data in signal
(MDIDO for master mode, MDODI for slave mode), the se-
rial data out signal (MDODI for master mode, MDIDO for
slave mode), and the serial clock (MSK).
In slave mode, an optional fourth signal (MWCS) may be
used to enable the slave transmit. At any given time, only
one slave can respond to the master. Each slave device has
its own chip select signal (MWCS) for this purpose.
Figure 48 shows a block diagram of the enhanced Microwire
serial interface in the device.
20.1 MICROWIRE OPERATION
The Microwire interface allows several devices to be con-
nected on one three-wire system. At any given time, one of
these devices operates as the master while all other devices
operate as slaves. The Microwire interface allows the device
to operate either as a master or slave transferring 8- or 16-
bits of data.
The master device supplies the synchronous clock (MSK)
for the serial interface and initiates the data transfer. The
slave devices respond by sending (or receiving) the re-
quested data. Each slave device uses the master’s clock for
serially shifting data out (or in), while the master shifts the
data in (or out).
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