ORSPI4 datasheet(55/263 Pages) LATTICE

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Lattice Semiconductor

ORCA ORSPI4 Data Sheet

The Transmit Calendar also broadcasts the BURST_VAL, current status and either the transmit Calendar entry

vector or a user-conﬁgurable port value to the FPGA. Selection between the Calendar vector and the conﬁgured

value is decided with the 'M'-bit. When logic '0', the Calendar Port vector is broadcast to the FPGA. Otherwise, the

user-conﬁgurable PORT_ID ﬁeld is sent. The optional PORT_ID is provided in order to assist the FPGA in mapping

it's proprietary channel/port numbers to the SPI4 Calendar port value. By conﬁguring the PORT_ID value and set-

ting the 'M'-bit for particular ports, the FPGA will receive the programmed value instead of the SPI4 port number.

This feature is very useful when the user is sharing a particular FIFO partition within the DPRAM between multiple

ports. Providing these ﬁelds to the FPGA enables users to updated statistics of port servicing for external data

schedulers and the external Memory Controller.

• If the user desires to have proprietary channel/port values broadcast to the FPGA, the 'M'-bit must be set to a

logical “1”, and the associated PORT_ID ﬁeld must be conﬁgured to the desired value.

• This is done on a per port basis, so some ports may be mapped, while others use the Transmit Calendar index

vector.

• If the user maps more than one port to the same FIFO partition, the user is free to choose which Port ID ﬁeld is

sent to the FPGA.

As ports are serviced, their Credit ﬁelds are updated according to the requirements as deﬁned within the SPI4

speciﬁcation. Although not commonly used, the Transmit SPI4 Calendar logic allows the user to conﬁgure the

Credit ﬁeld with an initial value at conﬁguration time. This is useful for some applications as well as providing diag-

nostic and test capabilities of the Calendar update logic. The Transmit Calendar also supports single Maxburst1 &

Maxburst2 values, as deﬁned within SPI4. The MB_EN ﬁeld is enabled on a per-port basis and indicates whether

the associated port differentiates between the deﬁned Hungry and Starving states. When the MB_EN bit is set to a

logical “1”, that particular port uses both the Maxburst1 and Maxburst2 ﬁelds: otherwise only the Maxburst1 ﬁeld is

associated with the Port’s Credit ﬁeld update algorithm.

• In order to use the Maxburst1 and Maxburst2 ﬁelds, the user must program both ﬁelds to the required values. By

default the value for these registers is “0”.

• The user must either conﬁgure the MB_EN ﬁeld for each port to a logical “1” if the port have it’s Credit ﬁeld

updated using the Maxburst2 ﬁeld. By default the Maxburst2 values are not used in the Credit update calculation.

• The user can optionally conﬁgure the Credit ﬁeld to a particular value if desired, although it is not necessary for

most applications.

During normal operation, Transmit status is received on a per port basis. The status ﬁeld for each port is updated

independent of where the Transmit Calendar polling exists. Internal logic prevents updates to be performed on a

port while it is in use. Although uncommon, the SPI4 Transmit Calendar allows the user to conﬁgure the STAT ﬁeld

to some value, but only during initialization. This is intended to be used for diagnostics or for some other proprietary

applications. Under normal operation, the user can ignore this function.

• The user can program the STAT[1:0] ﬁeld for as many ports as desired within the PDM.

When a HUNGRY status indication is received, transfers up to Maxburst2 16-byte blocks or the remainder of what

was previously granted (whichever is greater) may be sent to the corresponding port prior to the next status update.

A STARVING status indication 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 prior to

the next status update. Internal to ORSPI4, the “16-byte blocks” term is also called BURST_VAL. Even though the

Maxburst1 and Maxburst2 are global parameters for all the ports, each port has its own BURST_VAL parameter

attached to it that the user must program in the Transmit Port Descriptor Memory (TXPDM). Every time the TX sta-

tus is updated for a port, Maxburst1 or Maxburst2 values are loaded into the credits ﬁeld for that particular port.

From that point on until a new TX status update takes place, data is sent according to the following ﬂow-chart.

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