HCS08 datasheet(316/374 Pages) NXP

316 / 374 page

Universal Serial Bus Device Controller (S08USBV1)

MC9S08JM60 Series Data Sheet, Rev. 5

316

Freescale Semiconductor

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How much data was transmitted or received.

•

Where the buffer resides in buffer memory

The BDT is composed of buffer descriptors (BD) which are used to define and control the actual buffers

in the USB RAM space. BDs always occur as a 3-bytes block. See Figure 17-19 for the BD example of

Endpoint 0 IN start from USB RAM offset 0x00.

The format for the buffer descriptor is shown in Table 17-22.

Offset

0x00

OWN

DATA0/1

BDTKPID[3] BDTKPID[3] BDTKPID[1] BDTKPID[0]

DTS

BDTSTALL

0x01

BC[7:0]

0x02

EPADR[9:4]

Figure 17-19. Buffer Descriptor Example

Table 17-22. Buffer Descriptor Table Fields

Field

Description

OWN

OWN — This OWN bit determines who currently owns the buffer. The USB SIE generally writes a 0 to this bit

when it has completed a token. The USB module ignores all other fields in the BD when OWN=0. Once the BD

has been assigned to the USB module (OWN=1), the MCU must not change it in any way. This byte of the BD

must always be the last byte the MCU (firmware) updates when it initializes a BD. Although the hardware will

not block the MCU from accessing the BD while owned by the USB SIE, doing so may cause undefined

behavior and is generally not recommended.

0 The MCU has exclusive access to the entire BD

1 The USB module has exclusive access to the BD

DATA0/1

Data Toggle — This bit defines if a DATA0 field (DATA0/1=0) or a DATA1 (DATA0/1=1) field was transmitted or

received. It is unchanged by the USB module.

Data 0 packet

1 Data 1 packet

BDTKPID[3:0]

The current token PID is written back to the BD by the USB module when a transfer completes. The values

written back are the token PID values from the USB specification: 0x1 for an OUT token, 0x9 for and IN token

or 0xd for a SETUP token.

DTS

Data Toggle Synchronization— This bit enables data toggle synchronization.

0 No data toggle synchronization is performed.

1 Data toggle synchronization is performed.

BDTSTALL

BDT Stall — Setting this bit will cause the USB module to issue a STALL handshake if a token is received by

the SIE that would use the BDT in this location. The BDT is not consumed by the SIE (the OWN bit remains

and the rest of the BD is unchanged) when the BDTSTALL bit is set.

0 BDT stall is disabled

1 USB will issue a STALL handshake if a token is received by the SIE that would use the BDT in this location

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