AN2131SC Cypress Semiconductor Corp, AN2131SC Datasheet - Page 182

• Manufacturer Part Number: AN2131SC
• Description: IC MCU 8051 8K RAM 24MHZ 44QFP
• Manufacturer: Cypress Semiconductor Corp
• Series: EZ-USB®r

Specifications of AN2131SC

• Applications: USB Microcontroller
• Core Processor: 8051
• Program Memory Type: ROMless
• Controller Series: AN213x
• Ram Size: 8K x 8
• Interface: I²C, USB
• Number Of I /o: 16
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 428-1306; AN2131SC

From Table 10-1, at power-on:
The EZ-USB register bit CPUCS.0 resets the 8051. This bit is HI at power-on, initially
holding the 8051 in reset. There are three ways to release the 8051 from reset:
EZ-USB TRM v1.9
10.3
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Endpoint data buffers and byte counts are un-initialized (1,2).
The 8051 is held in reset, and the CLK24 pin is enabled (3).
All port pins are configured as input ports (4-6).
USB interrupts are disabled, and USB interrupt requests are cleared (7-8).
Bulk IN and OUT endpoints are unarmed, and their stall bits are cleared (9). The
EZ-USB core will NAK IN or OUT tokens while the 8051 is reset. OUT end-
points are enabled when the 8051 is released from reset.
Endpoint toggle bits are cleared (11).
The ReNum bit is cleared. This means that the EZ-USB core, and not the 8051,
initially responds to USB device requests (12).
The USB function address register is set to zero (13).
The endpoint valid bits are set to match the endpoints used by the default USB
device (14-17).
Endpoint pairing is disabled. Also, ISOSend0=0, meaning that if an Isochronous
endpoint receives an IN token without being loaded by the 8051 in the previous
frame, the EZ-USB core does not generate any response (18).
The breakpoint condition is cleared, and autovectoring is turned off (19).
Configuration Zero, Alternate Setting Zero is in effect (20-21).
By the host, as the final step of a RAM download.
Automatically, as part of an EEPROM load.
Automatically, when external ROM is used (EA=1).
Releasing the 8051 Reset
Chapter 10. EZ-USB Resets
Page 10-3