SL811HS
Table 16. SOF Counter LOW Address when Written [Address 0Eh]
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SOF7
SOF6
SOF5
SOF4
SOF3
SOF2
SOF1
SOF0
Example: To set up SOF for 1 ms interval, SOF counter register 0Eh should be set to E0h.
SOF Counter High/Control Register 2 [Address = 0Fh]. When read, this register returns the value of the SOF counter divided by
64. The software must use this register to determine the available bandwidth in the current frame before initiating any USB transfer.
In this way, the user is able to avoid babble conditions on the USB. For example, to determine the available bandwidth left in a frame
do the following.
Maximum number of clock ticks in 1 ms time frame is 12000 (1 count per 12 MHz clock period, or approximately 84 ns.) The value
read back in Register 0FH is the (count × 64) × 84 ns = time remaining in current frame. USB bit time = one 12 MHz period.
Value of register 0FH Available bit times left are between
BBH
BAH
12000 bits to 11968 (187 × 64) bits
11968 bits to 11904 (186 × 64) bits
Note: Any write to the 0Fh register clears the internal frame counter. Write register 0Fh at least once after power-up. The internal
frame counter is incremented after every SOF timer tick. The internal frame counter is an 11-bit counter, which is used to track the
frame number. The frame number is incremented after each timer tick. Its contents are transmitted to the slave every millisecond in
a SOF packet.
Table 17. SOF High Counter when Read [Address 0Fh]
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
C13
C12
C11
C10
C9
C8
C7
C6
When writing to this register the bits definition are defined as follows.
Table 18. Control Register 2 when Written [Address 0Fh]
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SL811HS
SL811HS
SOF High Counter Register
Master/Slave D+/D– Data
selection
Polarity Swap
Bit Position
Bit Name
Function
7
6
SL811HS Master/Slave selection
Master = 1, Slave = 0.
SL811HS D+/D– Data Polarity Swap
’1’ = change polarity (low speed)
’0’ = no change of polarity (full speed).
5-0
SOF High Counter Register
Write a value or read it back to SOF High Counter Register.
Note Any write to Control register 0Fh enables the SL811HS full
features bit. This is an internal bit of the SL811HS that enables
additional features.
hardware SOF generation. To load both HIGH and LOW
registers with the proper values, the user must follow this
sequence:
1. Write E0h to register 0Eh. This sets the lower byte of the SOF
counter
The USB-B register set is used when SL811HS full feature bit is
enabled.
2. Write AEh to register 0Fh, AEh configures the part for full
speed (no change of polarity) Host with bits 5–0 = 2Eh for
upper portion of SOF counter.
Example. To set up host to generate 1 ms SOF time:
The register 0Fh contains the upper 6 bits of the SOF timer.
Register 0Eh contains the lower 8 bits of the SOF timer. The
timer is based on an internal 12 MHz clock and uses a counter,
which counts down to zero from an initial value. To set the timer
for 1 ms time, the register 0Eh is loaded with value E0h and
register 0Fh (bits 0–5) is loaded with 2Eh. To start the timer, bit
0 of register 05h (Control Register 1) is set to ’1’, which enables
3. Enablebit 0 in register 05h. Thisenableshardwaregeneration
of SOF.
4. Set the ARM bit at address 00h. This starts the SOF
generation.
Document 38-08008 Rev. *F
Page 13 of 32
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