USB on-the-go full-speed (OTG_FS) RM0351
1768/1830 DocID024597 Rev 5
Once the MAC receives an IN token, this information (token received) is synchronized to the
AHB clock by the PFC (the PFC runs on the AHB clock). The PFC then reads the data from
the SPRAM and writes them into the dual clock source buffer. The MAC then reads the data
out of the source buffer (4 deep).
If the AHB is running at a higher frequency than the PHY, the application can use a smaller
value for TRDT (in OTG_GUSBCFG).
Figure 537 has the following signals:
• tkn_rcvd: Token received information from MAC to PFC
• dynced_tkn_rcvd: Doubled sync tkn_rcvd, from PCLK to HCLK domain
• spr_read: Read to SPRAM
• spr_addr: Address to SPRAM
• spr_rdata: Read data from SPRAM
• srcbuf_push: Push to the source buffer
• srcbuf_rdata: Read data from the source buffer. Data seen by MAC
To calculate the value of TRDT, refer to
Table 307: TRDT values(FS).
Figure 537. TRDT max timing case
NS NS NS NS NS
(#,+
0#,+
TKN?RCVD
SYNCED?TKN?RCVD
SPR?READ
SPR?ADDR
SPR?RDATA
SRCBUF?PUSH
SRCBUF?RDATA
#LOCKS
$
!
$
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