Motorola MPC8260 - Manual (Page 770)

28-12 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
0x0C RBASE Word RxBD base address (must be divisible by eight). DeÞnes the starting location in the
memory map for the FCC RxBDs. This provides great ßexibility in how FCC RxBDs are
partitioned. By selecting RBASE entries for all FCCs and by setting the W bit in the last
BD in each BD table, the user can select how many BDs to allocate for the receive side
of every FCC. The user must initialize RBASE before enabling the corresponding
channel. Furthermore, the user should not conÞgure BD tables of two enabled FCCs to
overlap or erratic operation occurs.
0x10 RBDSTAT Hword RxBD status and control. Reserved for CP use only.
0x12 RBDLEN Hword RxBD data length. A down-count value initialized by the CP with MRBLR and
decremented with every byte written by the SDMA channels.
0x14 RDPTR Word RxBD data pointer. Updated by the SDMA channels to show the next address in the
buffer to be accessed.
0x18 TSTATE Word Tx internal state. The high byte, TSTATE[0Ð7], contains the function code register; see
Section 28.7.1, ÒFCC Function Code Registers (FCRx).Ó TSTATE[8Ð31] is used by the
CP and must be cleared initially.
0x1C TBASE Word TxBD base address (must be divisible by eight). DeÞnes the starting location in the
memory map for the FCC TxBDs. This provides great ßexibility in how FCC TxBDs are
partitioned. By selecting TBASE entries for all FCCs and by setting the W bit in the last
BD in each BD table, the user can select how many BDs to allocate for the transmit side
of every FCC. The user must initialize TBASE before enabling the corresponding
channel. Furthermore, the user should not conÞgure BD tables of two enabled FCCs to
overlap or erratic operation occurs.
0x20 TBDSTAT Hword TxBD status and control. Reserved for CP use only.
0x22 TBDLEN Hword TxBD data length. A down-count value initialized with the TxBD data length and
decremented with every byte read by the SDMA channels.
0x24 TDPTR Word TxBD data pointer. Updated by the SDMA channels to show the next address in the
buffer to be accessed.
0x28 RBPTR Word RxBD pointer. Points to the next BD that the receiver transfers data to when it is in idle
state or to the current BD during frame processing. After a reset or when the end of the
BD table is reached, the CP sets RBPTR = RBASE. Although the user need never write
to RBPTR in most applications, the user can modify it when the receiver is disabled or
when no receive buffer is in use.
0x2C TBPTR Word TxBD pointer. Points either to the next BD that the transmitter transfers data from when it
is in idle state or to the current BD during frame transmission. After a reset or when the
end of the BD table is reached, the CP sets TBPTR = TBASE. Although the user need
never write to TBPTR in most applications, the user can modify it when the transmitter is
disabled or when no transmit buffer is in use (after a
STOP TRANSMIT or GRACEFUL STOP
TRANSMIT command is issued and the frame completes transmission).
0x30 RCRC Word Temporary receive CRC
0x34 TCRC Word Temporary transmit CRC
0x38 First word of protocol-speciÞc area
1 Offset from FCC base: 0x8400 (FCC1), 0x8500 (FCC2) and 0x8600 (FCC3); see Section 13.5.2, ÒParameter RAM.Ó
Table 28-5. FCC Parameter RAM Common to All Protocols (Continued)
Offset 1 Name Width Description