296Chapter 7 Controller Board“Cajun” Bus InterfaceThe “Cajun” bus connects the DC and the EC. The EC uses this bus toaccess DC resources, including the semaphore registers. (The semaphoreregisters are the primary communications path between the EC and DC.)PortsThe V8 ASIC controls the following I/O functions:• Interface to IEEE® 1284 Level 2 host• Interface to RS-232-E serial host• Interface to RS-422-B serial hostAll the circuitry required for these types of hosts is provided on the controllerboard, except for the drivers themselves, ESD protection, and terminations.Host I/O Drivers and TerminationBeyond the MPC8245 processor and V8 ASIC, additional support circuitrycompletes the serial and parallel interfaces. These circuits include:• RS-232 drivers and receivers. These circuits use internal charge pumpsto eliminate the need for ± 12V power.• RS-422 differential drivers and receivers• Parallel port pull-up and pull-down terminating resistors in DIPconfiguration for easy removal and installation.All interface ICs and terminations have the following characteristics:• Provide ESD protection to 15KV for all inputs.• Less than 0.05V common mode ripple, measured at the power andground of the interface ICs.• Less than 0.02V common mode ripple, measured between chassisground and the ground pins of the interface ICs.• Greater than 200V/μs slew rate for all outputs.Engine ControllerThe engine controller (EC) consists of four main elements:• 80C167 Micro controller• 128KB 5.0V-only FLASH program memory, organized as 64K x 16 bits.This memory is not expandable.• MECA (Mechanism Engine Control ASIC)• Analog drive circuitry
