Freescale Semiconductor POWERPC MPC860T - Manual (Page 43)

MOTOROLA Chapter 6. Programming Model 6-11
PRELIMINARYÑSUBJECT TO CHANGE WITHOUT NOTICE
Table 6-12 describes R_DES_ACTIVE Þelds.
6.2.12 TxBD Active Register (X_DES_ACTIVE)
The TxBD active register, shown in Figure 6-12, is a command register that the user should
write to indicate that the TxBD ring was updated (transmit buffers have been produced by
the software driver with TxBD[R] set).
Whenever the register is written, X_DES_ACTIVE is set, regardless of the data written by
the user. When the bit is set, the TxBD ring is polled and transmit frames (provided
ECNTRL[ETHER_EN] is also set) are processed. Once a TxBD whose ownership bit is not
set is polled, X_DES_ACTIVE is cleared and polling stops until the bit is set, signifying
additional BDs have been placed into the TxBD ring.
X_DES_ACTIVE is cleared at reset and by clearing ECNTRL[ETHER_EN].
Bits 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Field Ñ R_DES_ACTIVE Ñ
Reset 0000_0000_0000_0000
R/W Read/write
Addr 0xE50
Bits 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Field 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Reset 0000_0000_0000_0000
R/W Read/write
Addr 0xE52
Figure 6-11. R_DES_ACTIVE Register
Table 6-12. R_DES_ACTIVE Field Descriptions
Bits Name Description
0Р6 С Reserved.
7 R_DES_ACTIVE Signals the FEC that empty buffers are available. Set when this register is written,
regardless of the value written. Cleared by the FEC whenever no additional BDs are
ready in the RxBD ring.
8Р31 С Reserved.
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..