CS8900A-CQZR Cirrus Logic Inc, CS8900A-CQZR Datasheet - Page 94

• Manufacturer Part Number: CS8900A-CQZR
• Description: Ethernet ICs IC 10Mbps Ethernet Controller 5V
• Manufacturer: Cirrus Logic Inc

Specifications of CS8900A-CQZR

• Ethernet Connection Type: 10Base- 2, 10Base- 5, 10Base- F, 10Base- T
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Product: Ethernet Controllers
• Standard Supported: IEEE 802.3
• Data Rate: 10 Mbps
• Maximum Operating Temperature: + 70 C
• Package / Case: LQFP-100
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5.4 Auto-Switch DMA
5.4.1 Overview
The CS8900A supports a unique feature,
Auto-Switch DMA, that allows it to switch be-
tween Memory or I/O mode and Receive DMA
automatically. Auto-Switch DMA allows the
CS8900A to realize the performance advan-
tages of Memory or I/O mode while minimizing
the number of missed frames that could result
due to slow processing by the host.
5.4.2 Configuring the CS8900A for Auto-
Switch DMA
Auto-Switch DMA mode requires the same
configuration as Receive-DMA-only mode,
with one exception: the AutoRxDMAE bit
(Register 3, RxCFG, Bit A) must be set, and
94
Read the DMA frame Count (C
Host Enters Interrupt Routine
(PacketPage base + 0028h)
CIRRUS LOGIC PRODUCT DATASHEET
Figure 25. RxDMA Only Operation
C
Yes
Process the
DMA
No
RxDMA
bit set?
Frame
C
= 0 ?
DMA
Frames
Yes
No
the RxDMAonly bit (Register 3, RxCFG, Bit 9)
must be clear (see Section 5.3 on page 90,
Configuring the CS8900A for DMA Operation).
In Auto-Switch DMA mode, the CS8900A op-
erates in non-DMA mode if possible, only
switching to slave DMA if necessary.
Note that if the AutoRxDMAE bit and the RxD-
MAonly bit (Register 3, RxCFG, bit 9) are both
set, the CS8900A uses DMA for all receive
frames.
5.4.3 Auto-Switch DMA Operation
Whenever a frame begins to be received in
Auto-Switch DMA mode, the CS8900A checks
to see if there is enough on-chip buffer space
to store a maximum length frame. If there is,
the incoming frame is pre-processed and buff-
DMA
)
Process other events
that caused interrupt
Process other events
that caused interrupt
Crystal LAN™ Ethernet Controller
CS8900A
DS271F5