ST7260E1 STMicroelectronics, ST7260E1 Datasheet - Page 98

• Manufacturer Part Number: ST7260E1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 8K FLASH/ROM AND SERIAL COMMUNICATION INTERFACE (SCI)
• Manufacturer: STMicroelectronics

Specifications of ST7260E1

• 4 Or 8 Kbytes Program Memory: high density Flash (HDFlash), or FastROM with readout and write protection

USB interface (USB)
14.5.2
14.5.3
Note:
14.5.4
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1.
2.
3.
4.
Initializing DMA buffers
The DMA buffers are a contiguous zone of memory whose maximum size is 48 bytes. They
can be placed anywhere in the memory space to enable the reception of messages. The 10
most significant bits of the start of this memory area are specified by bits DA15-DA6 in
registers DMAR and IDR, the remaining bits are 0. The memory map is shown in
Each buffer is filled starting from the bottom (last 3 address bits=000) up.
Endpoint initialization
To be ready to receive:
Set STAT_RX to VALID (11b) in EP0RB to enable reception.
To be ready to transmit:
1.
2.
3.
Once transmission and/or reception are enabled, registers EPnRA and/or EPnRB
(respectively) must not be modified by software, as the hardware can change their value on
the fly.
When the operation is completed, they can be accessed again to enable a new operation.
Interrupt handling
Start of frame (SOF)
The interrupt service routine may monitor the SOF events for a 1 ms synchronization event
to the USB bus. This interrupt is generated at the end of a resume sequence and can also
be used to detect this event.
USB reset (RESET)
When this event occurs, the DADDR register is reset, and communication is disabled in all
endpoint registers (the USB interface will not respond to any packet). Software is
responsible for reenabling endpoint 0 within 10 ms of the end of reset. To do this, set the
STAT_RX bits in the EP0RB register to VALID.
Suspend (SUSP)
The CPU is warned about the lack of bus activity for more than 3 ms, which is a suspend
request. The software should set the USB interface to suspend mode and execute an ST7
HALT instruction to meet the USB-specified power constraints.
Initialize the DMAR, IDR, and IMR registers (choice of enabled interrupts, address of
DMA buffers). Refer the paragraph titled initializing the DMA Buffers.
Initialize the EP0RA and EP0RB registers to enable accesses to address 0 and
endpoint 0 to support USB enumeration. Refer to the paragraph titled Endpoint
Initialization.
When addresses are received through this channel, update the content of the DADDR.
If needed, write the endpoint numbers in the EA fields in the EP1RB and EP2RB
register.
Write the data in the DMA transmit buffer.
In register EPnRA, specify the number of bytes to be transmitted in the TBC field
Enable the endpoint by setting the STAT_TX bits to VALID (11b) in EPnRA.
ST7260xx
Figure
42.