CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 77

• Manufacturer Part Number: CN8237EBGB
• Description: ATM SAR 622Mbps 3.3V ABR/CBR/GFR/UBR/VBR 456-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8237EBGB

• Package: 456BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 622 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.135 V

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
3.3.2 Write-only Status Queues
28237-DSH-001-C
3.3.2.1 Control
3.3.2.2 Queue
Management
Variables
The SAR reports status to the host through write-only status queues. Both the
segmentation and reassembly coprocessors use their own format of status queue.
However, the CN8237 manages all status queues with the same algorithm.
word-aligned (8-byte) status queue base addresses. To support multiple clients,
the CN8237 provides 32 queues of each type. The SAR and host manage each
queue independently through queue management variables. The SAR stores its
variables in internal base table registers. The host maintains its variables in its
driver. Each queue contains a programmable number of queue entries.
Table 3-3
Table 3-3. Write-only Status Queue Variables
Figure 3-4
all of the variables described in
to the host by writing a status queue entry. After it writes the entry, the CN8237
increments its write pointer (WRITE++). This write also triggers a maskable
interrupt.
queue. The VLD bit in each queue entry enables polling. The SAR sets the VLD
bit equal to 1 when it writes a status queue entry. The host resets it to 0 after
processing an entry.
WRITE
READ_UD
READ
INTERVAL
UPDATE
READ_UD_PNTR
These queues reside in host memory. The host must assign double
The SAR maintains its own write pointer, WRITE. The CN8237 reports status
The host either responds to this interrupt, or periodically polls the status
Variable
Mindspeed Technologies
describes the variables for write-only status queue management.
illustrates the status queue management algorithm. The host initializes
Current SAR position
in queue
Last known host
position in queue as
seen by SAR
Current host position
in queue
Number of queue
entries processed by
host before writing
READ_UD
Number of queue
entries since last write
of READ_UD
Host pointer to
READ_UD
Definition
Table
3-3.
™
SAR Base table
SAR Base table
Host Variable
Host Variable
Host Variable
Host Variable
Location
3.3 Write-only Control and Status
3.0 Host Interface
Initialization
Host defined
&READ_UD
0
0
0
0
3-7