SAB-C165 SIEMENS [Siemens Semiconductor Group], SAB-C165 Datasheet - Page 20

• Manufacturer Part Number: SAB-C165
• Description: C16x-Family of High-Performance CMOS 16-Bit Microcontrollers
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

C165
Serial Channels
Serial communication with other microcontrollers, processors, terminals or external peripheral
components is provided by two serial interfaces with different functionality, an Asynchronous/
Synchronous Serial Channel (ASC0) and a High-Speed Synchronous Serial Channel (SSC).
They are upward compatible with the serial ports of the Siemens SAB 8051x microcontroller family
and support full-duplex asynchronous communication up to 625 KBaud and half-duplex
synchronous communication up to 5 Mbaud (2.5 Mbaud on the ASC0) @ 20-MHz system clock.
Two dedicated baud rate generators allow to set up all standard baud rates without oscillator tuning.
For transmission, reception, and erroneous reception 3 separate interrupt vectors are provided for
each serial channel.
In asynchronous mode, 8- or 9-bit data frames are transmitted or received, preceded by a start bit
and terminated by one or two stop bits. For multiprocessor communication, a mechanism to
distinguish address from data bytes has been included (8-bit data + wake up bit mode).
In synchronous mode, the ASC0 transmits or receives bytes (8 bits) synchronously to a shift clock
which is generated by the ASC0. The SSC transmits or receives characters of 2...16 bits length
synchronously to a shift clock which can be generated by the SSC (master mode) or by an external
master (slave mode). The SSC can start shifting with the LSB or with the MSB, while the ASC0
always shifts the LSB first.
A loop back option is available for testing purposes.
A number of optional hardware error detection capabilities has been included to increase the
reliability of data transfers. A parity bit can automatically be generated on transmission or be
checked on reception. Framing error detection allows to recognize data frames with missing stop
bits. An overrun error will be generated, if the last character received has not been read out of the
receive buffer register at the time the reception of a new character is complete.
Watchdog Timer
The Watchdog Timer represents one of the fail-safe mechanisms which have been implemented to
prevent the controller from malfunctioning for longer periods of time.
The Watchdog Timer is always enabled after a reset of the chip, and can only be disabled in the time
interval until the EINIT (end of initialization) instruction has been executed. Thus, the chip’s start-up
procedure is always monitored. The software has to be designed to service the Watchdog Timer
before it overflows. If, due to hardware or software related failures, the software fails to do so, the
Watchdog Timer overflows and generates an internal hardware reset and pulls the RSTOUT pin low
in order to allow external hardware components to be reset.
The Watchdog Timer is a 16-bit timer, clocked with the system clock divided either by 2 or by 128.
The high byte of the Watchdog Timer register can be set to a prespecified reload value (stored in
WDTREL) in order to allow further variation of the monitored time interval. Each time it is serviced
by the application software, the high byte of the Watchdog Timer is reloaded. Thus, time intervals
between 25 s and 420 ms can be monitored (@ 20 MHz). The default Watchdog Timer interval
after reset is 6.55 ms (@ 20 MHz).
Semiconductor Group
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