AN2131SC Cypress Semiconductor Corp, AN2131SC Datasheet - Page 175

• 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

Figure 9-7 illustrates an ISR that services endpoint 2-OUT. When endpoint 2-OUT
requires service, the EZ-USB core activates the USB interrupt request, vectoring the 8051
to location 0x43. The jump instruction at this location, which was originally coded as
“LJMP 04-00” becomes “LJMP 04-2C” due to the EZ-USB core substituting 2C as the
Autovector byte for Endpoint 2-OUT (Table 9-3). The 8051 jumps to 042C, where it exe-
cutes the jump instruction to the endpoint 2-OUT ISR shown in this example at address
0119. Once the 8051 takes the vector at 0043, initiation of the endpoint-specific ISR takes
only eight 8051 cycles.
Page 9-12
AVEC
0043
0044
0045
2. Code the jump table with jump instructions to each individual USB interrupt ser-
vice routine. This table has two important requirements, arising from the format of
the AVEC byte (zero-based, with 2 LSBs set to 0):
•
•
•
•
It must begin on a page boundary (address 0xNN00).
The jump instructions must be four bytes apart.
The interrupt service routines can be placed anywhere in memory.
Write initialization code to enable the USB interrupt (INT2), and Autovector-
ing.
8051 USB
Interrupt
Vector
(00)2C
LJMP
2C
04
USB core
Figure 9-7. The Autovector Mechanism in Action
Chapter 9. EZ-USB Interrupts
042C
042D
042E
0400
USB_Jmp_Table:
LJMP EP2OUT_ISR
01
19
0119
EP2OUT_ISR:
EZ-USB TRM v1.9