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ORCA ORSPI4 Data Sheet

Figure 20. Port Credit Field Update Flow Chart

Table 9 below shows the SPI4 Status update deﬁnitions.

Table 9. SPI4 Status Field Deﬁnition

When transmitting across the SPI4 link, typically for clock speeds in excess of 350 MHz, dynamic alignment is

required to maintain a coherent data link. In conjunction with dynamic alignment, SPI4 outlines a Training protocol

that is periodically used to maintain receive data integrity. The SPI4 Transmit core supports data training through

the use of a 32-bit variable named TX_DATA_MAX_T. This 32-bit variable indicates the number of clock cycles that

will occur between training sequences. SPI4 also deﬁnes an TX_ALPHA variable indicating the number of times

the training pattern is to be repeated during a training session. The TDP supports both these variables allowing the

user to tailor both of these parameters to ﬁt their particular environment and dynamic trafﬁc requirements.

• The user must conﬁgure the 32-bit TX_DATA_MAX_T variable to indicate the number of clock cycles that should

lapse between training sequence. A value of 0x00000000 disables training. By default training is disabled.

MSB

LSB

Description:

Reserved for framing or indicate a disabled status link.

SATISFIED Indicates the corresponding port's FIFO is almost full. When SATISFIED is

received, only transfers using the remaining previously granted 16-byte blocks (if any) may

be sent to corresponding port until the next status update. No additional transfers to that

port are permitted while SATISFIED is indicated.

HUNGRY When HUNGRY is received, transfers for up to MAXBURST2 16-byte blocks or

the remainder of what was previously granted (whichever is greater), may be sent to the

corresponding port until the next status update.

STARVING Indicates that buffer underﬂow is imminent in the corresponding PHY port.

When STARVING is received, transfers for up to MAXBURST1 16-byte blocks may be

sent to the corresponding port until the next status update.

START

STATUS

UPDATE

STATUS

MB_EN

Credits = Maxburst1

Credits = Maxburst2

Data Sent =

BURST_VAL * 128 Bits

Data Sent =

| (Credits - BURST_VAL) | * 128 Bits

Credits = | (Credits - BURST_VAL) |

YES

HUNGRY

SATISFIED

STARVING

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