PIC18F97J60 Datasheet, PDF (237/474 Pages) Microchip Technology – 64/80/100-Pin, High-Performance, 1 Mbit Flash Microcontrollers with Ethernet

PIC18F97J60 FAMILY
18.5.2 TRANSMITTING PACKETS
The Ethernet module’s MAC will automatically
generate the preamble and Start-of-Frame delimiter
fields when transmitting. Additionally, the MAC can
generate any padding (if needed) and the CRC if
configured to do so. The application must generate and
write all other frame fields into the buffer memory for
transmission.
In addition, the Ethernet module requires a single
per-packet control byte to precede the packet for trans-
mission. The control byte is organized as shown in
Figure 18-7. Before transmitting packets, the MAC
registers, which alter the transmission characteristics,
should be initialized as documented in Section 18.4
“Module Initialization”.
FIGURE 18-7:
FORMAT FOR PER-PACKET CONTROL BYTES
—
—
—
—
PHUGEEN PPADN PCRCEN POVERRIDE
bit 7
bit 0
bit 7-4
bit 3
bit 2
bit 1
bit 0
Unused
PHUGEEN: Per-Packet Huge Frame Enable bit
When POVERRIDE = 1:
1 = The packet will be transmitted in whole
0 = The MAC will transmit up to the number of bytes specified by MAMXFL. If the packet is
larger than MAMXFL, it will be aborted after MAMXFL is reached.
When POVERRIDE = 0:
This bit is ignored.
PPADN: Per-Packet Padding Enable bit
When POVERRIDE = 1:
1 = The packet will be zero padded to 60 bytes if it is less than 60 bytes
0 = The packet will be transmitted without adding any padding bytes
When POVERRIDE = 0:
This bit is ignored.
PCRCEN: Per-Packet CRC Enable bit
When POVERRIDE = 1:
1 = A valid CRC will be calculated and attached to the frame
0 = No CRC will be appended. The last 4 bytes of the frame will be checked for validity as a
CRC.
When POVERRIDE = 0:
This bit is ignored.
POVERRIDE: Per-Packet Override bit
1 = The values of PCRCEN, PPADN and PHUGEEN will override the configuration defined by
MACON3
0 = The values in MACON3 will be used to determine how the packet will be transmitted
© 2006 Microchip Technology Inc.
Advance Information
DS39762A-page 235