153 lines
3.6 KiB
C
153 lines
3.6 KiB
C
#include "gba.h"
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//only need this file if connector is present on the device
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#ifdef GB_CONN
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uint16_t cur_addr_lo;
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uint8_t cur_addr_hi;
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//=================================================================================================
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//
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// GBA operations
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// This file includes all the gba functions possible to be called from the gba dictionary.
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//
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// See description of the commands contained here in shared/shared_dictionaries.h
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//
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//=================================================================================================
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/* Desc:Function takes an opcode which was transmitted via USB
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* then decodes it to call designated function.
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* shared_dict_gba.h is used in both host and fw to ensure opcodes/names align
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* Pre: Macros must be defined in firmware pinport.h
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* opcode must be defined in shared_dict_gba.h
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* Post:function call complete.
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* Rtn: SUCCESS if opcode found and completed, error if opcode not present or other problem.
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*/
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uint8_t gba_call( uint8_t opcode, uint8_t miscdata, uint16_t operand, uint8_t *rdata )
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{
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#define RD_LEN 0
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#define RD0 1
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#define RD1 2
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//resist temptation to make these 16bit indexes
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//will break rule of accessing usb_buff in half word aligned access
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//would have to use RD1-RD2 for 16bit aligned access..
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//Actually.. that's not true. return & RD_LEN are index 0-1, so RD0-1 would be index 2-3
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//so it should be half word aligned..
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#define BYTE_LEN 1
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#define HWORD_LEN 2
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switch (opcode) {
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// //no return value:
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case LATCH_ADDR:
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//operand A0-15, miscdata A16-23->D0-7
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gba_latch_addr( operand, miscdata );
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break;
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case RELEASE_BUS:
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ROMSEL_HI();
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DATA_IP(); //A16-23 are output here during reads
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break;
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//8bit return values:
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case GBA_RD:
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//address must have been latched already
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rdata[RD_LEN] = HWORD_LEN;
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//can use operand as a variable
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operand = gba_rd();
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rdata[RD0] = operand;
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rdata[RD1] = operand>>8;
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break;
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default:
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//macro doesn't exist
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return ERR_UNKN_GBA_OPCODE;
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}
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return SUCCESS;
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}
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//latches A0-23, leaves /CS low for subsequent accesses
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void gba_latch_addr( uint16_t addr_lo, uint8_t addr_hi)
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{
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//store address so other functions can keep track of incrementing
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cur_addr_lo = addr_lo;
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cur_addr_hi = addr_hi;
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//set addr & data bus to output
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ADDR_OP();
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DATA_OP();
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//place addr on the bus
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ADDR_SET(addr_lo);
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DATA_SET(addr_hi);
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//latch the address
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//leave it low for subsequent access
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ROMSEL_LO();
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//leave AD0-15 as input for subsequent access
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ADDR_IP();
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//leave A16-23 as output for subsequent access
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return;
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}
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//address must already have been latched
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//will increment address variables and A16-23
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//ready to read next byte
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uint16_t gba_rd()
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{
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uint16_t read;
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if( cur_addr_lo == 0xFFFF ) {
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//going to have a roll over when incrementing
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cur_addr_hi++;
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//don't output it till this access is done though
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}
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CSRD_LO();
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cur_addr_lo++; //increment to next byte that will be read
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read = ADDR_VAL;
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CSRD_HI();
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//if we had a 16bit addr roll over, need to increment A16-23
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DATA_SET(cur_addr_hi);
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return read;
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}
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//can only read 255 bytes, len can't be 255 else it would create infinite loop
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// I think the byte read version is actually slightly faster...?
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uint8_t gba_page_rd( uint16_t *data, uint8_t len)
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{
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uint8_t i;
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uint16_t read;
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for( i=0; i<=len; i++ ) {
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//usbPoll(); //Call usbdrv.h usb polling while waiting for data
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//read 16bits
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read = gba_rd();
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//store lower byte little endian
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//now stores entire 16bit read at once
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data[i] = read;
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//upper byte
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//i++;
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//store upper byte
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//data[i] = read>>8;
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}
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//return index of last byte read
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return i;
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}
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#endif //GB_CONN
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