ST72651AR6 STMicroelectronics, ST72651AR6 Datasheet - Page 67

• Manufacturer Part Number: ST72651AR6
• Description: LOW-POWER, FULL-SPEED USB 8-BIT MCU WITH 32K FLASH, 5K RAM, FLASH CARD I/F, TIMER, PWM, ADC, I2C, SPI
• Manufacturer: STMicroelectronics

Specifications of ST72651AR6

• Dual Supply Management: analog voltage detector on the USB power line to enable smart power switching from USB power to battery (on E suffix devices).
• Programmable Internal Voltage Regulator For Memory Cards (2.8v To 3.5v) Supplying: Flash Card I/O lines (voltage shifting)
• 5 Usb Endpoints: 1 control endpoint
• Dtc (data Transfer Coprocessor): Universal Serial/Parallel communications interface, with software plug-ins for current and future protocol standards

USB INTERFACE (Cont’d)
11.3.7 Register Description
BUFFER
(BUFCSR)
Read Only (except bit 0, read/write)
Reset Value: 0000 0000 (00h)
Bits 7:4 = Reserved, forced by hardware to 0.
Bit 3 = BUFNUM Current USB Buffer Number
This bit is set and cleared by hardware. When data
are received by Endpoint 2 in normal mode (refer
to the description of the MOD[1:0] bits in the
EP2RXR register) it indicates which buffer con-
tains the data.
0: Current buffer is Buffer 0
1: Current buffer is Buffer 1
Bits 2:1 = STATB[1:0] Buffer Status Bits
These bits are set and cleared by hardware. When
data are transmitted or received by Endpoint 2 in
upload or download mode (refer to the description
of the MOD[1:0] bits in the EP2RXR register) the
STATB[1:0] bits indicate the status as follows:
Bit 0 = CLR Clear Buffer Status
This bit is written by software to clear the BUF-
NUM and STATB[1:0] bits (it also resets the pack-
et counter of the Buffer Manager state machine). It
can be used to re-initialize the upload/download
flow (refer to the description of the MOD[1:0] bits in
the EP2RXR register).
0: No effect
1: Clear BUFNUM and STATB[1:0] bits
Download
7
0
Upload
Mode
Mode
0
Buffer n not full (USB waiting to
read Buffer n)
Buffer n full (USB can upload this
buffer)
Buffer n empty (Can be written to
by USB)
Buffer n not empty (USB waiting
to write to this buffer)
CONTROL/STATUS
0
Meaning
0
BUF-
NUM
STAT
B1
REGISTER
STAT
B0
STATBn
Value
Doc ID 7215 Rev 4
0
1
0
1
CLR
0
INTERRUPT STATUS REGISTER (ISTR)
Read/Write
Reset Value: 0000 0000 (00h)
These bits cannot be set by software. When an in-
terrupt occurs these bits are set by hardware. Soft-
ware must read them to determine the interrupt
type and clear them after servicing.
Note: The CTR bit (which is an OR of all the end-
point CTR flags) cannot be cleared directly, only
by clearing the CTR flags in the Endpoint regis-
ters.
Bit 7 = CTR Correct Transfer.
This bit is set by hardware when a correct transfer
operation is performed. This bit is an OR of all
CTR flags (CTR0 in the EP0R register and
CTR_RX and CTR_TX in the EPnR registers). By
looking in the USBSR register, the type of transfer
can be determined from the PID[1:0] bits for End-
point 0. For the other Endpoints, the Endpoint
number on which the transfer was made is identi-
fied by the EP[1:0] bits and the type of transfer by
the IN/OUT bit.
0: No Correct Transfer detected
1: Correct Transfer detected
Note: A transfer where the device sent a NAK or
STALL handshake is considered not correct (the
host only sends ACK handshakes). A transfer is
considered correct if there are no errors in the PID
and CRC fields, if the DATA0/DATA1 PID is sent
as expected, if there were no data overruns, bit
stuffing or framing errors.
Bit 6 = Reserved, forced by hardware to 0.
Bit 5 = SOVR Setup Overrun.
This bit is set by hardware when a correct Setup
transfer operation is performed while the software
is servicing an interrupt which occurred on the
same Endpoint (CTR0 bit in the EP0R register is
still set when SETUP correct transfer occurs).
0: No SETUP overrun detected
1: SETUP overrun detected
When this event occurs, the USBSR register is not
updated because the only source of the SOVR
event is the SETUP token reception on the Control
Endpoint (EP0).
CTR
7
0
SOVR ERROR SUSP ESUSP RESET SOF
ST72651AR6
67/161
0
1