Rainbow Electronics AT89C5131 - Manual (Page 138)

138
AT89C5131
4136A–USB–03/03
Reset Value = 00h
Table 89. UEPSTAX (S:CEh) USB Endpoint X Status Register
7 6 5 4 3 2 1 0
DIR RXOUTB1 STALLRQ TXRDY STL/CRC RXSETUP RXOUTB0 TXCMP
Bit Number
Bit
Mnemonic Description
7 DIR
Control Endpoint Direction
This bit is used only if the endpoint is configured in the control type (seeSection “UEPCONX Register UEPCONX (S:D4h)
USB Endpoint X Control Register”).
This bit determines the Control data and status direction.
The device firmware will set this bit ONLY for the IN data stage, before any other USB operation. Otherwise, the device
firmware will clear this bit.
6 RXOUTB1
Received OUT Data Bank 1 for Endpoints 4, 5 and 6 (Ping-pong mode)
This bit is set by hardware after a new packet has been stored in the endpoint FIFO data bank 1 (only in Ping-pong mode).
Then, the endpoint interrupt is triggered if enabled (see“UEPINT Register UEPINT (S:F8h read-only) USB Endpoint
Interrupt Register” on page 142) and all the following OUT packets to the endpoint bank 1 are rejected (NAK’ed) until this
bit has been cleared, excepted for Isochronous Endpoints.
This bit will be cleared by the device firmware after reading the OUT data from the endpoint FIFO.
5 STALLRQ
Stall Handshake Request
Set this bit to request a STALL answer to the host for the next handshake.Clear this bit otherwise.
For CONTROL endpoints: cleared by hardware when a valid SETUP PID is received.
4 TXRDY
TX Packet Ready
Set this bit after a packet has been written into the endpoint FIFO for IN data transfers. Data will be written into the
endpoint FIFO only after this bit has been cleared. Set this bit without writing data to the endpoint FIFO to send a Zero
Length Packet.
This bit is cleared by hardware, as soon as the packet has been sent for Isochronous endpoints, or after the host has
acknowledged the packet for Control, Bulk and Interrupt endpoints. When this bit is cleared, the endpoint interrupt is
triggered if enabled (see“UEPINT Register UEPINT (S:F8h read-only) USB Endpoint Interrupt Register” on page 142).
3 STLCRC
Stall Sent/CRC error flag
- For Control, Bulk and Interrupt Endpoints:
This bit is set by hardware after a STALL handshake has been sent as requested by STALLRQ. Then, the endpoint
interrupt is triggered if enabled (see“UEPINT Register UEPINT (S:F8h read-only) USB Endpoint Interrupt Register” on
page 142)
It will be cleared by the device firmware.
- For Isochronous Endpoints (Read-Only):
This bit is set by hardware if the last received data is corrupted (CRC error on data).
This bit is updated by hardware when a new data is received.
2 RXSETUP
Received SETUP
This bit is set by hardware when a valid SETUP packet has been received from the host. Then, all the other bits of the
register are cleared by hardware and the endpoint interrupt is triggered if enabled (see“UEPINT Register UEPINT (S:F8h
read-only) USB Endpoint Interrupt Register” on page 142).
It will be cleared by the device firmware after reading the SETUP data from the endpoint FIFO.
1 RXOUTB0
Received OUT Data Bank 0 (see also RXOUTB1 bit for Ping-pong Endpoints)
This bit is set by hardware after a new packet has been stored in the endpoint FIFO data bank 0. Then, the endpoint
interrupt is triggered if enabled (see“UEPINT Register UEPINT (S:F8h read-only) USB Endpoint Interrupt Register” on
page 142) and all the following OUT packets to the endpoint bank 0 are rejected (NAK’ed) until this bit has been cleared,
excepted for Isochronous Endpoints. However, for control endpoints, an early SETUP transaction may overwrite the
content of the endpoint FIFO, even if its Data packet is received while this bit is set.
This bit will be cleared by the device firmware after reading the OUT data from the endpoint FIFO.
0 TXCMPL
Transmitted IN Data Complete
This bit is set by hardware after an IN packet has been transmitted for Isochronous endpoints and after it has been
accepted (ACK’ed) by the host for Control, Bulk and Interrupt endpoints. Then, the endpoint interrupt is triggered if
enabled (see“UEPINT Register UEPINT (S:F8h read-only) USB Endpoint Interrupt Register” on page 142).
This bit will be cleared by the device firmware before setting TXRDY.