public void Write(byte val)
{
try
{
if (((val ^ m_prev) & SCL) != 0) // clock edge, data in/out
{
if ((val & SCL) != 0) // nvram reads SDA
{
if (m_state == NVSTATE.RD_ACK)
{
if ((val & SDA) != 0) // no ACK, stop
{
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
// move next byte to host
m_state = NVSTATE.SEND_DATA;
m_dataout = m_nvram[m_address];
m_address = (m_address + 1) & 0x7FF;
m_bitsout = 0;
//goto exit; // out_z==1;
return;
}
if (((1 << (int)m_state) & ((1 << (int)NVSTATE.RCV_ADDR) | (1 << (int)NVSTATE.RCV_CMD) | (1 << (int)NVSTATE.RCV_DATA))) != 0)
{
if (m_out_z != 0) // skip nvram ACK before reading
{
m_datain = (byte)(2 * m_datain + ((val >> SDA_SHIFT_IN) & 1));
m_bitsin++;
}
}
}
else
{ // nvram sets SDA
if (m_bitsin == 8) // byte received
{
m_bitsin = 0;
if (m_state == NVSTATE.RCV_CMD)
{
if ((m_datain & 0xF0) != 0xA0)
{
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
m_address = (m_address & 0xFF) + ((m_datain << 7) & 0x700);
if ((m_datain & 1) != 0)
{ // read from current address
m_dataout = m_nvram[m_address];
m_address = (m_address + 1) & 0x7FF;
m_bitsout = 0;
m_state = NVSTATE.SEND_DATA;
}
else
{
m_state = NVSTATE.RCV_ADDR;
}
}
else if (m_state == NVSTATE.RCV_ADDR)
{
m_address = (m_address & 0x700) + m_datain;
m_state = NVSTATE.RCV_DATA;
m_bitsin = 0;
}
else if (m_state == NVSTATE.RCV_DATA)
{
m_nvram[m_address] = m_datain;
m_address = (m_address & 0x7F0) + ((m_address + 1) & 0x0F);
// state unchanged
}
// EEPROM always acknowledges
m_out = SDA_0;
m_out_z = 0;
//goto exit;
return;
}
if (m_state == NVSTATE.SEND_DATA)
{
if (m_bitsout == 8)
{
m_state = NVSTATE.RD_ACK;
m_out_z = 1;
//goto exit;
return;
}
m_out = (byte)((m_dataout & 0x80) != 0 ? SDA_1 : SDA_0);
m_dataout *= 2;
m_bitsout++;
m_out_z = 0;
//goto exit;
return;
}
m_out_z = 1; // no ACK, reading
}
//goto exit;
return;
}
if ((val & SCL) != 0 && ((val ^ m_prev) & SDA) != 0) // start/stop
{
if ((val & SDA) != 0)
{ // stop
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
else
{
m_state = NVSTATE.RCV_CMD;
m_bitsin = 0; // start
}
m_out_z = 1;
}
// else SDA changed on low SCL
}
finally
{
if (m_out_z != 0)
{
m_out = (byte)((val & SDA) != 0 ? SDA_1 : SDA_0);
}
m_prev = val;
}
}
public void Write(byte val)
{
try
{
if (((val ^ m_prev) & SCL) != 0) // clock edge, data in/out
{
if ((val & SCL) != 0) // nvram reads SDA
{
if (m_state == NVSTATE.RD_ACK)
{
if ((val & SDA) != 0) // no ACK, stop
{
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
// move next byte to host
m_state = NVSTATE.SEND_DATA;
m_dataout = m_nvram[m_address];
m_address = (m_address + 1) & 0x7FF;
m_bitsout = 0;
//goto exit; // out_z==1;
return;
}
if (((1 << (int)m_state) & ((1 << (int)NVSTATE.RCV_ADDR) | (1 << (int)NVSTATE.RCV_CMD) | (1 << (int)NVSTATE.RCV_DATA))) != 0)
{
if (m_out_z != 0) // skip nvram ACK before reading
{
m_datain = (byte)(2 * m_datain + ((val >> SDA_SHIFT_IN) & 1));
m_bitsin++;
}
}
}
else
{ // nvram sets SDA
if (m_bitsin == 8) // byte received
{
m_bitsin = 0;
if (m_state == NVSTATE.RCV_CMD)
{
if ((m_datain & 0xF0) != 0xA0)
{
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
m_address = (m_address & 0xFF) + ((m_datain << 7) & 0x700);
if ((m_datain & 1) != 0)
{ // read from current address
m_dataout = m_nvram[m_address];
m_address = (m_address + 1) & 0x7FF;
m_bitsout = 0;
m_state = NVSTATE.SEND_DATA;
}
else
{
m_state = NVSTATE.RCV_ADDR;
}
}
else if (m_state == NVSTATE.RCV_ADDR)
{
m_address = (m_address & 0x700) + m_datain;
m_state = NVSTATE.RCV_DATA;
m_bitsin = 0;
}
else if (m_state == NVSTATE.RCV_DATA)
{
m_nvram[m_address] = m_datain;
m_address = (m_address & 0x7F0) + ((m_address + 1) & 0x0F);
// state unchanged
}
// EEPROM always acknowledges
m_out = SDA_0;
m_out_z = 0;
//goto exit;
return;
}
if (m_state == NVSTATE.SEND_DATA)
{
if (m_bitsout == 8)
{
m_state = NVSTATE.RD_ACK;
m_out_z = 1;
//goto exit;
return;
}
m_out = (byte)((m_dataout & 0x80) != 0 ? SDA_1 : SDA_0);
m_dataout *= 2;
m_bitsout++;
m_out_z = 0;
//goto exit;
return;
}
m_out_z = 1; // no ACK, reading
}
//goto exit;
return;
}
if ((val & SCL) != 0 && ((val ^ m_prev) & SDA) != 0) // start/stop
{
if ((val & SDA) != 0)
{ // stop
// goto idle;
m_state = NVSTATE.IDLE;
m_out_z = 1;
return;
}
else
{
m_state = NVSTATE.RCV_CMD;
m_bitsin = 0; // start
}
m_out_z = 1;
}
// else SDA changed on low SCL
}
finally
{
if (m_out_z != 0)
{
m_out = (byte)((val & SDA) != 0 ? SDA_1 : SDA_0);
}
m_prev = val;
}
}
