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99 lines
3.2 KiB
C
99 lines
3.2 KiB
C
/*
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* external_mem.h
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*
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* Created on: Nov 25, 2011
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* Author: Doug
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*/
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#ifndef EXTERNAL_MEM_H_
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#define EXTERNAL_MEM_H_
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#include <stdint.h>
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#include <stdbool.h>
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// Holds info about the chip (retrieved with JEDEC standards)
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struct ChipID
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{
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uint8_t manufacturerID;
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uint8_t deviceID;
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};
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// Masks for functions that want a chip...
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#define IC1 (1 << 3)
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#define IC2 (1 << 2)
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#define IC3 (1 << 1)
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#define IC4 (1 << 0)
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#define ALL_CHIPS (IC1 | IC2 | IC3 | IC4)
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// I feel kind of sick making these available to the outside world, but
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// I'm doing it for efficiency.
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// These are the bits on port B corresponding to the control signals.
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// Pass them to ExternalMem_Assert() or ExternalMem_Deassert().
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#define SIMM_WE (1 << 6)
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#define SIMM_OE (1 << 5)
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#define SIMM_CS (1 << 4)
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// Initializes the (bit-banged) external memory interface
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void ExternalMem_Init(void);
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// Sets the value outputted to the address lines
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void ExternalMem_SetAddress(uint32_t address);
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// Sets the value outputted to the data lines
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void ExternalMem_SetData(uint32_t data);
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// Sets the value outputted to the address and data lines
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void ExternalMem_SetAddressAndData(uint32_t address, uint32_t data);
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// Puts the data lines into input mode, for reading back stored data
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void ExternalMem_SetDataAsInput(void);
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// Reads back the value the chips are putting onto the data lines
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uint32_t ExternalMem_ReadData(void);
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/*// Sets the state of the chip select line
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void ExternalMem_AssertCS(void);
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void ExternalMem_DeassertCS(void);
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// Sets the state of the write enable line
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void ExternalMem_AssertWE(void);
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void ExternalMem_DeassertWE(void);
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// Sets the state of the output enable line
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void ExternalMem_AssertOE(void);
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void ExternalMem_DeassertOE(void);*/
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// This is not the nicest-looking software engineering practice
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// in the world, but it saves needlessly wasted CPU cycles
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// that would be wasted in layers upon layers of abstraction
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#define ExternalMem_Assert(assertMask) PORTB &= ~(assertMask);
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#define ExternalMem_Deassert(assertMask) PORTB |= (assertMask);
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// Reads a set of data from all 4 chips simultaneously
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void ExternalMem_Read(uint32_t startAddress, uint32_t *buf, uint32_t len);
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// Performs a single write cycle on all 4 chips simultaneously
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void ExternalMem_WriteCycle(uint32_t address, uint32_t data);
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// Performs a single read cycle on all 4 chips simultaneously
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uint32_t ExternalMem_ReadCycle(uint32_t address);
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// Does an unlock sequence on the chips requested
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void ExternalMem_UnlockChips(uint8_t chipsMask);
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// Identifies the chips that are currently in the SIMM
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void ExternalMem_IdentifyChips(struct ChipID *chips);
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// Erases the chips requested
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void ExternalMem_EraseChips(uint8_t chipsMask);
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// Writes a byte to the chips requested at the specified address
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void ExternalMem_WriteByteToChips(uint32_t address, uint32_t data, uint8_t chipsMask);
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// Writes a buffer to the requested chips simultaneously
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// (each uint32_t contains an 8-bit portion for each chip,
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// which is masked away if the chip is not requested)
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void ExternalMem_Write(uint32_t startAddress, uint32_t *buf, uint32_t len, uint8_t chipsMask);
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#endif /* EXTERNAL_MEM_H_ */
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