TSS463 ATMEL Corporation, TSS463 Datasheet - Page 11

• Manufacturer Part Number: TSS463
• Description: VAN Data Link Controller with Serial Interface
• Manufacturer: ATMEL Corporation

Figure 8. SCI Speed Considerations
Interrupts
Reset
Asynchronous Reset
Synchronous Reset
4102E–AUTO–12/04
SCLK
MOSI
SS
(4 s at 1 MHz)
4 Xtal Min
125 Kbits/s Max for SCLK
Start Bit
If an event occurs in the TSS463B that needs the attention of the processor, this will be
signalled on the active low, open drain interrupt request pin. The event that creates this
request is controlled by the internal registers.
Every time the microprocessor accesses any of the interrupt registers (addresses 0x08
to 0x0B), the INT pin will be released momentarily. This enables the TSS463B to work
with processors that have either edge or level sensitive interrupt inputs.
The reset is applied asynchronously or synchronously to the XTAL clock.
It can be done either by the RESET pin (hardware asynchronous reset) or by software
(software asynchronous reset).
The RESET pin is a CMOS trigger input with a pull-up resistor (~ 70 k ). An external
1 F capacitor to GND provides to RESET pin an efficient behavior.
The asynchronous software reset is made by the ’Initialization Sequence’described in
“Motorola SPI Mode” on page 5.
Two ’0x00’bytes provide an asynchronous software reset and configure the TSS463B in
the Motorola SPI mode while two ’0xFF’bytes provide a reset and configure the compo-
nent in the Intel SPI mode and ’0x00 followed by 0xFF ’provide a reset and configure the
component in the SCI mode. The SS pin must be asserted as shown on Figure 9. The
SPI/SCI logic will monitor these two bytes and provide an internal reset pulse asserting
the TSS463B in the right mode.
A synchronous reset (regarding XTAL clock) is available on the TSS463B during current
operation. It is made through the GRES command bit of the Command Register
(address 0x03).
The two kinds of reset are ordered and filtered. Then the internal reset, always asserted
asynchronously, enables the internal oscillator. Then it waits for 12 clock periods and
the oscillator stability.
The different blocks of the TSS463B need to be turned on synchronously. So the
release of the internal reset is synchronous and a loose of clock can let the TSS463B in
permanent reset after applying Reset.
It is important to note that even after a reset on the RESET pin, the user should wait for
12 clock periods before sending the ’Initialization Sequence’in order to select the SPI or
SCI mode (because the default mode after a hardware reset is the Motorola SPI mode).
Address
(8 s at 1 MHz)
8 Xtal Min
Stop Bit
Control
(15 s at 1 MHz)
15 Xtal Min
Data
(12 s at 1 MHz)
12 Xtal Min
TSS463B
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