CX11656 HomePlug 1.0 PHY Data Sheet
3.2.1.2
GPSI DC Characteristics
The GSPI DC characteristics are listed in Table 3-4.
Table 3-4. GPSI DC Characteristics
Parameter
Symbol
Parameter Name
Test
Min
Max
Unit
Condition
Receive Timing
tGPSI_RPER
tGPSI_RHIGH
tGPSI_RLOW
tGPSI_RSU
tGPSI_RDH
tGPSI_RRXENH
GPSI RXCLK Period
GPSI RXCLK High Time
GPSI RXCLK Low Time
GPSI_RXD and GPSI_RXEN Setup to ↑ GPSI_RXCLK
GPSI_RXD Hold after ↑ GPSI_RXCLK
GPSI_RXEN Hold after ↓ GPSI_RXCLK
Transmit Timing
@ 1.5 V
@ 1.5 V
@ 1.5 V
@ 1.5 V
@ 1.5 V
@ 1.5 V
99.99
40
40
15
15
100.01
60
60
ns
ns
ns
ns
ns
ns
0
tGPSI_TPER
GPSI TXCLK Period
GPSI TXCLK High Time
GPSI_TXD and GPSI_TXEN Delay from ↑ GPSI_TXCLK
GPSI_RXEN Hold after ↓ GPSI_TXEN
@ 1.5 V
@ 1.5 V
@ 1.5 V
@ 1.5 V
99.99
40
0
100.01
60
70
ns
ns
ns
ns
tGPSI_THIGH
tGPSI_TDELAY
tGPSI_TRXENH
0
3.2.1.3
GPSI Signal Descriptions
GPSI_TXCLK and GPSI_RXCLK: The CX11656 generates a stable, continuous 10
MHz square wave that is supplied on GPSI_TXCLK and GPSI_RXCLK. These clocks
provide the timing reference for the transfer of the GPSI_TXEN and GPSI_TXD signal,
as well as GPSI_RXEN and GPSI_RXD.
GPSI_RXD: GPSI_RXD contains the data recovered from the medium by the CX11656
and transitions synchronously with respect to GPSI_RXCLK. The CX11656 properly
formats the frame such that the external host controller will be presented with the
expected preamble plus SFD.
GPSI_RXEN: GPSI_RXEN is asserted by the CX11656 to indicate that the CX11656
has decoded receive data to present to the external host controller.
GPSI_TXBSY: GPSI_TXBSY is an optionally used signal to tell the external host
controller when the CX11656 is available for sending packets. When a packet is being
transmitted, GPSI_TXBSY is held high. GPSI_TXBSY will go low whenever the
CX11656 is ready to send another packet. If this signal is not used, the transmitting logic
must pace the packet transmissions to ensure that no packets are lost due to buffer
overflow.
On transmit, the CX11656 asserts GPSI_TXBSY sometime after GPSI_TXEN becomes
active, and drops GPSI_TXBSY after GPSI_TXEN goes inactive AND when the
CX11656 is ready to accept another packet for transmission. When GPSI_TXBSY falls,
the external host controller may assert GPSI_TXEN again if there is another packet to
send.
GPSI_TXBSY does not affect nor reflect the receive side of the channel. Once packets
start arriving off of the powerline medium and begin transmission to the external host
controller over the GPSI interface, the external host controller MUST be ready to receive
or the packet can be lost.
GPSI_TXEN: GPSI_TXEN from the external host provides the framing for the Ethernet
packet. An active GPSI_TXEN indicates to the CX11656 that data on GPSI_TXD should
be sampled using GPSI_TXCLK.
3-14
Conexant Proprietary and Confidential Information
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