Document Number: 002-xxxxx Rev. **
Page 21 of 42
PRELIMINARY
CYBLE-013025-00
CYBLE-013030-00
Peripheral Transport Unit
Broadcom Serial Communications Interface
The CYBLE-0130XX-00 provides a 2-pin master BSC interface, which can be used to retrieve configuration information from an
external EEPROM or to communicate with peripherals such as track-ball or touch-pad modules, and motion tracking ICs used in
mouse devices. The BSC interface is compatible with I
2
C slave devices. The BSC does not support multimaster capability or flexible
wait-state insertion by either master or slave devices.
The following transfer clock rates are supported by the BSC:
n
100 kHz
n
400 kHz
n
800 kHz (not a standard I
2
C-compatible speed.)
n
1 MHz (Compatibility with high-speed I
2
C-compatible devices is not guaranteed.)
The following transfer types are supported by the BSC:
n
Read (Up to 16 bytes can be read.)
n
Write (Up to 16 bytes can be written.)
n
Read-then-Write (Up to 16 bytes can be read and up to 16 bytes can be written.)
n
Write-then-Read (Up to 16 bytes can be written and up to 16 bytes can be read.)
Hardware controls the transfers, requiring minimal firmware setup and supervision.
The clock pin (SCL) and data pin (SDA) are both open-drain I/O pins. Pull-up resistors external to the CYBLE-0130XX-00 are required
on both the SCL and SDA pins for proper operation.
USupport for changing the baud rate during normal HCI UART operation is included through a vendor-specific command that allows
the host to adjust the contents of the baud rate registers.
The CYBLE-0130XX-00 UART operates correctly with the host UART as long as the combined baud rate error of the two devices is
within ±5%.
Clock Frequencies
Peripheral Block
The peripheral blocks of the CYBLE-0130XX-00 all run from a single 128 kHz low-power RC oscillator. The oscillator can be turned
on at the request of any of the peripherals. If the peripheral is not enabled, it shall not assert its clock request line.
The keyboard scanner is a special case, in that it may drop its clock request line even when enabled, and then reassert the clock
request line if a keypress is detected.
32 kHz Crystal Oscillator
shows the 32 kHz crystal (XTAL) oscillator with external components and
lists the oscillator’s
characteristics. It is a standard Pierce oscillator using a comparator with hysteresis on the output to create a
single-ended digital output. The hysteresis was added to eliminate any chatter when the input is around the threshold
of the comparator and is ~100 mV. This circuit can be operated with a 32 kHz or 32.768 kHz crystal oscillator or be driven
with a clock input at similar frequency. The default component values are: R1 = 10 M?, C1 = C2 = ~10 pF. The values
of C1 and C2 are used to fine-tune the oscillator.
