CY7C66013
CY7C66113
Document #: 38-08024 Rev. *A
Page 41 of 58
Bits[6:0] of the endpoint 0 mode register are locked from CPU write operations whenever the SIE has updated one of these bits,
which the SIE does only at the end of the token phase of a transaction (SETUP... Data... ACK, OUT... Data... ACK, or IN... Data...
ACK). The CPU can unlock these bits by doing a subsequent read of this register. Only endpoint 0 mode registers are locked
when updated. The locking mechanism does not apply to the mode registers of other endpoints.
Because of these hardware locking features, firmware must perform an IORD after an IOWR to an endpoint 0 register. This verifies
that the contents have changed as desired, and that the SIE has not updated these values.
While the SETUP bit is set, the CPU cannot write to the endpoint zero FIFOs. This prevents firmware from overwriting an incoming
SETUP transaction before firmware has a chance to read the SETUP data. Refer to Table 19-1 for the appropriate endpoint zero
memory locations.
The Mode bits (bits [3:0]) control how the endpoint responds to USB bus traffic. The mode bit encoding is shown in Table 18-1.
Additional information on the mode bits can be found in Table 20-2 and Table 20-1.
Note: The SIE offers an “Ack out - Status in” mode and not an “Ack out - Nak in” mode. Therefore, if following the status stage
of a Control Write transfer a USB host were to immediately start the next transfer, the new Setup packet could override the data
payload of the data stage of the previous Control Write.
19.4
USB Non-Control Endpoint Mode Registers
The format of the non-control endpoint mode registers is shown in Figure 19-3.
USB Non-Control Device Endpoint Mode
ADDRESSES
0x14, 0x16, 0x44
Bits[3..0] : Mode
These sets the mode which control how the control endpoint responds to traffic. The mode bit encoding is shown in
Table 18-1.
Bit 4 : ACK
This bit is set whenever the SIE engages in a transaction to the register’s endpoint that completes with an ACK packet.
Bits[6..5] : Reserved
Must be written zero during register writes.
Bit 7 : STALL
If this STALL is set, the SIE stalls an OUT packet if the mode bits are set to ACK-IN, and the SIE stalls an IN packet if the
mode bits are set to ACK-OUT. For all other modes, the STALL bit must be a LOW.
19.5
USB Endpoint Counter Registers
There are five Endpoint Counter registers, with identical formats for both control and non-control endpoints. These registers
contain byte count information for USB transactions, as well as bits for data packet status. The format of these registers is shown
in Figure 19-4.
USB Endpoint Counter
ADDRESSES
0x11, 0x13, 0x15, 0x41, 0x43
Bits[5..0] : Byte Count
These counter bits indicate the number of data bytes in a transaction. For IN transactions, firmware loads the count with
the number of bytes to be transmitted to the host from the endpoint FIFO. Valid values are 0 to 32, inclusive. For OUT or
SETUP transactions, the count is updated by hardware to the number of data bytes received, plus two for the CRC bytes.
Valid values are 2 to 34, inclusive.
Bit #
7
654
321
0
Bit Name
STALL
Reserved
Reserved
ACK
Mode Bit 3
Mode Bit 2
Mode Bit 1
Mode Bit 0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
000
000
0
Figure 19-3. USB Non-Control Device Endpoint Mode Registers
Bit #
7
654
321
0
Bit Name
Data 0/1 Toggle Data Valid
Byte Count Bit
5
Byte Count Bit
4
Byte Count Bit
3
Byte Count Bit
2
Byte Count Bit
1
Byte Count Bit
0
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
000
000
0
Figure 19-4. USB Endpoint Counter Registers
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