M30240ECFP MITSUBISHI [Mitsubishi Electric Semiconductor], M30240ECFP Datasheet - Page 49

• Manufacturer Part Number: M30240ECFP
• Description: M30240 Group Specification
• Manufacturer: MITSUBISHI [Mitsubishi Electric Semiconductor]

Preliminary Specifications REV. E
Specifications in this manual are tentative and subject to change
Universal Serial Bus
Figure 1.30: USB Attach/Detach Register
2.18.4 USB Special Function Registers
2.18.3.3 Interrupt Endpoints:
2.18.4.1 USB Attach/Detach Register
The MCU controls USB operation through the use of special function registers (SFR). This section de-
scribes each USB related SFR. Some USB special function registers have a mix of read/write, read
only, and write only register bits. Additionally, the bits may be configured to allow the user to write only
a “0” or a “1” to individual bits.
• When accessing these registers, writing a “0” to a register that can only be set to a “1” by the CPU
• Writing a “1” to a register that can only be set to a “0” by the CPU has not effect on that register bit.
Each figure and description of the special function registers details this operation.
All USB Special Function Registers, with the exception of USB Attach/Detach (001F
trol (000C
033C
The contents of all USB Special Functions Registers, including USB Attach/Detach and USB Control,
are preserved on a software reset.
has no effect on that register bit.
Any endpoint can be used for interrupt transfers. For normal interrupt transfers, the interrupt transactions be-
have the same as bulk transactions, i.e., no special setting is required. The IN endpoints may also be used to
communicate rate feedback information for certain types of isochronous functions. This is done by setting the
INTPT bit in the IN CSR register of the corresponding endpoint.
The following outlines the operation sequence for an IN endpoint used to communicate rate feedback infor-
mation:
1. Set MAXP > 1/2 of the endpoint’s FIFO size;
2. Set INTPT bit of the IN CSR;
3. Flush the old data in the FIFO;
4. Load interrupt status information and set IN_PKT_RDY bit in the IN CSR;
5. Repeat steps 3 & 4 for all subsequent interrupt status updates.
The USB Attach / Detach Register is shown in Figure 1.30. The register is used to attach and detach the USB
function from a USB host without physically disconnecting the USB cable. This functionality is enabled by set-
ting P83_SECOND to a “1”. Doing this forces P83 to operate as a pull-up for D+ (through an external 1.5k
ohm resistor). The port driver is tri-stated and a “1” is always read from the port bit in this mode. When the
ATTACH/DETACH bit is a “1” (and P83_SECOND is a “1”), P83 is driven with the voltage on EXTCAP, caus-
ing D+ to be pulled up and the host to detect an attach. When the ATTACH/DETACH bit is a “0” (and
P83_SECOND is a “1”), P83 is tri-stated, causing D+ to be pulled down (through the cable and 15k ohm re-
sistor on the host/hub side) and a detach to be registered by the host. A 1.5k ohm pull-up resistor must be
connected externally from P83 to D+ when this functionality is used. When it is not used, the 1.5k ohm resistor
should be placed between EXTCAP and D+.
16
0 0 0 0 0 0
USB Attach/Detach Register
b7 b6 b5 b4 b3 b2 b1 b0
).
16
) must use byte access. Work access is prohibited for USB internal registers (0300
Bit symbol
Reserved
P83_2nd
Attach/
Detach
Symbol
USBAD
Attach/Detach
Port 83-Second
1-49
Bit name
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Address
0 : Normal mode for Port 8_3
1 : Forces Port 8_3 to operate as pull up for D+.
001F 16
0 : Tri-states, P8_3 causing the host to detect a detach
1 : Drives P8_3 with voltage on EXTCAP, causing the host
Must always be set to "0"
to detect an attach
Function
When reset
00 16
Mitsubishi microcomputers
M30240 Group
16
) and USB con-
R
W
16
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