DS33R11 Maxim Integrated Products, DS33R11 Datasheet - Page 53

• Manufacturer Part Number: DS33R11
• Description: Network Controller & Processor ICs Ethernet Mapper with Integrated T1-E1-J1
• Manufacturer: Maxim Integrated Products

Specifications of DS33R11

• Product: Framer
• Number Of Transceivers: 1
• Supply Voltage (max): 1.89 V, 3.465 V
• Supply Voltage (min): 1.71 V, 3.135 V
• Supply Current (max): 100 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Package / Case: BGA

9.13 Flow Control
Flow control may be required to ensure that data queues do not overflow and packets are not lost. The DS33R11
allows for optional flow control based on the queue high watermark or through host processor intervention. There
are 2 basic mechanisms that are used for flow control:
Note that the terms “transmit queue” and “receive queue” are with respect to the Ethernet Interface. The Receive
Queue is the queue for the data that arrives on the MII/RMII interface, is processed by the MAC and stored in the
SDRAM. Transmit queue is for data that arrives from the Serial port, is processed by the HDLC and stored in the
SDRAM to be sent to the MAC transmitter.
The following flow control options are possible:
Note that in order to use flow control, the receive queue size (in AR.RQSC1) must be 02h or greater. The receive
queue high threshold (in SU.RQHT) must be set to 01h or greater, but must be less than the queue size. If the high
threshold is set to the same value as the queue size, automatic flow control will not be effective. The high threshold
must always be set to less than the corresponding queue size.
The following table provides all the options on flow control mechanism for DS33R11.
Table 9-4. Options for Flow Control
Configuration
ATFLOW Bit
Pause Timer
JAME Bit
•
•
•
•
FCB Bit
(Pause)
FCE Bit
TYPE
In half duplex mode, a jam sequence is sent that causes collisions at the far end. The collisions cause the
transmitting node to reduce the rate of transmission.
In full duplex mode, flow control is initiated by the receiving node sending a pause frame. The pause frame
has a timer parameter that determines the pause timeout to be used by the transmitting node.
Automatic flow control can be enabled in software mode with the SU.GCR.ATFLOW bit. Note that the user
does not have control over SU.MACFCR.FCE and FCB bits if ATFLOW is set. The mechanism of sending
pause or jam is dependent only on the receive queue high threshold.
Manual flow control can be performed through software when SU.GCR.ATFLOW=0. The host processor
must monitor the receive queues and generate pause frames (full duplex) and/or jam bytes through the
SU.MACFCR.FCB, SU.GCR.JAME, and SU.MACFCR.FCE bits.
Half Duplex; Manual
Controlled By User
Controlled By User
Flow Control
N/A
N/A
0
Automatic Flow
Automatically
Automatically
Half Duplex;
Controlled
Controlled
Control
N/A
N/A
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MODE
Programmed by User
Full Duplex; Manual
Controlled By User
Controlled by User
Flow Control
N/A
0
Programmed by User
Automatic Flow
Automatically
Automatically
Full Duplex;
Controlled
Controlled
Control
N/A
1