Cirrus Logic CS8900A - Manual (Page 100)

100 DS271F5
CS8900A
Crystal LAN™ Ethernet Controller
CIRRUS LOGIC PRODUCT DATASHEET
the LineCTL register (Register 13) and is de-
scribed in Table 31.
Note that the CS8900A transmits in 10BASE-
T mode when no link pulses are being re-
ceived only if bit DisableLT is set in register
Test Control (Register 19).
5.6.2.2 Selecting which Events Cause Inter-
rupts
The TxCFG register (Register 7) and the Buf-
CFG register (Register B) are used to deter-
mine which transmit events will cause
interrupts to the host processor. Tables 32 and
33 describe the interrupt enable (iE) bits in
these registers.
5.6.3 Changing the Configuration
When the host configures these registers it
does not need to change them for subsequent
packet transmissions. If the host does choose
to change the TxCFG or BufCFG registers, it
may do so at any time. The effects of the
change are noticed immediately. That is, any
changes in the Interrupt Enable (iE) bits may
affect the packet currently being transmitted.
If the host chooses to change bits in the
LineCTL register after initialization, the Mod-
BackoffE bit and any receive related bit (LoRx-
Squelch, SerRxON) may be changed at any
time. However, the Auto AUI/10BT and AUIon-
ly bits should not be changed while the SerTx-
ON bit is set. If any of these three bits are to be
changed, the host should first clear the SerTx-
ON bit (Register 13, LineCTL, Bit 7), and then
set it when the changes are complete.
Register 13, LineCTL
Bit Bit Name Operation
7 SerTxON When set, transmission enabled.
8 AUIonly When set, AUI selected (takes
precedence over AutoAUI/10BT).
When clear, 10BASE-T selected.
9 AutoAUI/10BT When set, automatic interface
selection enabled.
B Mod
BackoffE
When set, the modified backoff
algorithm is used. When clear,
the standard backoff algorithm is
used.
D 2-part
DefDis
When set, two-part deferral is
disabled.
Table 31. Physical Interface Configuration
Register B, BufCFG
Bit Bit Name Operation
8 Rdy4TxiE When set, there is an interrupt
whenever buffer space becomes
available for a transmit frame
(used with a Transmit Request).
9 TxUnder
runiE
When set, there is an interrupt
whenever the CS8900A runs out
of data after transmit has started.
C TxCol
OvfloiE
When set, there is an interrupt
whenever the TxCol counter
overflows.
Table 33. Transmit Interrupt Configuration
Register 7, TxCFG
Bit Bit Name Operation
6 Loss-of-
CRSiE
When set, there is an interrupt
whenever the CS8900A fails to
detect Carrier Sense after trans-
mitting the preamble (applies to
the AUI only).
7 SQErroriE When set, there is an interrupt
whenever there is an SQE error.
8 TxOKiE When set, there is an interrupt
whenever a frame is transmitted
successfully..
9 Out-of-
windowiE
When set, there is an interrupt
whenever a late collision is
detected.
A JabberiE When set, there is an interrupt
whenever there is a jabber condi-
tion.
B AnycolliE When set, there is an interrupt
whenever there is a collision.
F 16colliE When set, there is an interrupt
whenever the CS8900A attempts
to transmit a single frame 16
times.
Table 32. Transmitting Interrupt Configuration