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ScramWorks• Design has evolved to higher capacity SRAM
• 1 or 2 chips for 8MB or 16MB capacity
• 3.3V circuitry
• 100% RamWorks compatibility
• AE and Nishida Radio video connectors
• Soon, and with brothers
Serial Segue• Communicates between computer systems
• Or between parts within a computer system
• Increasing replacing parallel communications
• USB
• Serial ATA
• PCI-e slots are serial busses
Serial Style• Asynchronous
• Rely on accurate timing on each end point
• Synchronous
• Clock is provided on the bus
• Flow Control
• In band
• Out of band
Serial - RS232• Super Serial Card, Apple IIc, 6551 ACIA
• Asynchronous
• In band and out of band flow control
• XON/XOFF, RTS/CTS
• Logic level and line level.
• 115,200Kbps to many megabits
Serial - intercomponent• Widely used in Arduino
• RTC, Stepper Motor, GPIO, Servo
• i2c
• SPI
• 1-wire
i2c• Inter-Integrated Circuit
• 2-wire, synchronous, half-duplex
• 10Khz, 100Khz, 400Khz modes
• Open-drain
• Multi-master capable
i2c• Data line - SDA
• Clock line - SCL
• Master drives clock
• All devices share data line
• Actual speed can be variable (0-100Khz)
i2c
(Image from Wikipedia)
Apple II - i2c ?
• Can it be done ?
• i2c allows slower speeds
• Ought to be easy!
• Where do we plug it in ?
Apple II Game Port
• 4 Annunciator outputs
• 3 Pushbutton inputs
• 4 Paddle Inputs
• 1 Utility Strobe
Apple II Game Port
Apple II Game Port
• Inputs and outputs are TTL
• But i2c is open drain
• Going to need some electronics!
Emitter Follower
Open Drain
Apple i2c - Schematic
• Two MOSFETs
• Two Resistors
• Two sets required to do both SDA and SCL
Apple i2c - SDA schematic
1243774
Apple i2c - Code• Some simple assembly language
• Merlin 8/16 (32?)
• Macros should help
• Ampersand extensions for Applesoft
Apple i2c - Code
AN0OFF EQU $C058 AN0ON EQU $C059 AN1OFF EQU $C05A AN1ON EQU $C05B
PB0 EQU $C061 PB1 EQU $C062 PB2 EQU $C063
Apple i2c - Code
SDAOFF MAC BIT AN0ON <<< SDAON MAC BIT AN0OFF <<< SCLOFF MAC BIT AN1ON <<< SCLON MAC BIT AN1OFF <<<
Apple i2c - CodeSCLSTAT MAC LDA PB1 <<< SCLWAIT MAC
WAIT SCLSTAT BMI WAIT
NOP <<< I2CSTART MAC
SDAOFF NOP NOP NOP NOP
SCLOFF <<< I2CCLOCK MAC
SCLON NOP NOP
SCLOFF NOP <<<
Summary
• Not working yet (sorry!)
• Questions ?
