AT32UC3C2512C Automotive Atmel Corporation, AT32UC3C2512C Automotive Datasheet - Page 502

• Manufacturer Part Number: AT32UC3C2512C Automotive
• Manufacturer: Atmel Corporation

24.6.3
24.6.4
24.6.5
24.6.6
9166C–AVR-08/11
Transmit Buffer List
Address Matching
Interrupts
Transmitting Frames
Transmit data is read from the system memory These buffers are listed in another data structure
that also resides in main memory. This data structure (Transmit Buffer Queue) is a sequence of
descriptor entries (as defined in
To create this list of buffers:
The MACB register-pair hash address and the four specific address register-pairs must be writ-
ten with the required values. Each register-pair comprises a bottom register and top register,
with the bottom register being written first. The address matching is disabled for a particular reg-
ister-pair after the bottom-register has been written and re-enabled when the top register is
written.
may be written at any time, regardless of whether the receive circuits are enabled or disabled.
There are 14 interrupt conditions that are detected within the MACB. These are ORed to make a
single interrupt. This interrupt is handled by the interrupt controller. On receipt of the interrupt
signal, the CPU enters the interrupt handler. To ascertain which interrupt has been generated,
read the interrupt status register. Note that this register clears itself when read. At reset, all inter-
rupts are disabled. To enable an interrupt, write to interrupt enable register with the pertinent
interrupt bit set to 1. To disable an interrupt, write to interrupt disable register with the pertinent
interrupt bit set to 1. To check whether an interrupt is enabled or disabled, read interrupt mask
register: if the bit is set to 1, the interrupt is disabled.
To set up a frame for transmission:
1. Allocate a number (n) of buffers of between 1 and 2047 bytes of data to be transmitted
2. Allocate an area 2n words for the transmit buffer descriptor entry in system memory
3. If fewer than 1024 buffers are defined, the last descriptor must be marked with the wrap
4. Write address of transmit buffer descriptor entry to MACB register transmit buffer queue
5. The transmit circuits can then be enabled by writing to the network control register.
1. Enable transmit in the network control register.
2. Allocate an area of system memory for transmit data. This does not have to be contigu-
3. Set-up the transmit buffer list.
4. Set the network control register to enable transmission and enable interrupts.
5. Write data for transmission into these buffers.
6. Write the address to transmit buffer descriptor queue pointer.
7. Write control and length to word one of the transmit buffer descriptor entry.
8. Write to the transmit start bit in the network control register.
in system memory. Up to 128 buffers per frame are allowed.
and create N entries in this list. Mark all entries in this list as owned by MACB, i.e. bit 31
of word 1 set to 0.
bit (bit 30 in word 1 set to 1).
pointer.
ous, varying byte lengths can be used as long as they conclude on byte borders.
See Section “24.5.8” on page 495.
Table 24-2 on page
for details of address matching. Each register-pair
492) that points to this data structure.
AT32UC3C
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