void sm510_base_device::op_lb()
{
// LB x: load BM/BL with 4-bit immediate value (partial)
m_bm = (m_bm & 0x04) | (m_param & 0x03);
m_bl = ((m_param >> 3) ^ (m_param >> 2)) & 0x01;
m_bl = (m_bl << 1) | m_bl;
m_bl <<= 2;
m_bl |= (m_param >> 2) & 0x03);
}
void sm511_device::op_lb()
{
// LB xy: load BL with y, BM with x; 2-bit immediate value each
// B_M1 <= I_2 in 1990 Sharp Microcontroller Data Book p.170 is a typo I think
m_bm = (m_bm & 0x04) | (m_param & 0x03);
m_bl = (m_bl & 0x0C) | ((m_param >> 2) & 0x03);
}
Did you try this naïve implementation already and saw that it failed, or what seems to be the issue? I think p170 in the data book must be a typo when it assigns B_M2 <= I2 instead of B_M2 <= I1...
EDIT: I think op_incb and op_decb also need attention. They currently skip the next instruction when they overflow. However, I think what the datasheet means is that B_L cannot overflow using these ops.
