diff options
Diffstat (limited to 'src/devices/machine/6821pia.h')
-rw-r--r-- | src/devices/machine/6821pia.h | 13 |
1 files changed, 5 insertions, 8 deletions
diff --git a/src/devices/machine/6821pia.h b/src/devices/machine/6821pia.h index 5682b43ecef..ad7d28f65d6 100644 --- a/src/devices/machine/6821pia.h +++ b/src/devices/machine/6821pia.h @@ -5,13 +5,10 @@ Motorola 6821 PIA interface and emulation Notes: - * get_port_b_z_mask() gives the caller the bitmask that shows + * port_b_z_mask() gives the caller the bitmask that shows which bits are high-impedance when reading port B, and thus - neither 0 or 1. get_output_cb2_z() returns the same info + neither 0 or 1. cb2_output_z() returns the same info for the CB2 pin. - * set_port_a_z_mask allows the input callback to indicate - which port A bits are disconnected. For these bits, the - read operation will return the output buffer's contents. * The 'alt' interface functions are used when the A0 and A1 address bits are swapped. * All 'int' data or return values are bool, and should be @@ -61,13 +58,13 @@ public: void write_alt(offs_t offset, uint8_t data) { write(((offset << 1) & 0x02) | ((offset >> 1) & 0x01), data); } uint8_t port_b_z_mask() const { return ~m_ddr_b; } // see first note in .c - void set_port_a_z_mask(uint8_t data) { m_port_a_z_mask = data; }// see second note in .c DECLARE_WRITE8_MEMBER( porta_w ) { write_porta(data); } void write_porta(uint8_t data); void write_porta_line(int line, bool state); - void set_a_input(uint8_t data, uint8_t z_mask); + void set_a_input(uint8_t data); uint8_t a_output(); + void set_port_a_input_overrides_output_mask(uint8_t mask) { m_a_input_overrides_output_mask = mask; } DECLARE_WRITE_LINE_MEMBER( pa0_w ) { write_porta_line(0, state); } DECLARE_WRITE_LINE_MEMBER( pa1_w ) { write_porta_line(1, state); } @@ -176,8 +173,8 @@ private: uint8_t m_in_ca1; uint8_t m_in_ca2; uint8_t m_out_a; + uint8_t m_a_input_overrides_output_mask; uint8_t m_out_ca2; - uint8_t m_port_a_z_mask; uint8_t m_ddr_a; uint8_t m_ctl_a; uint8_t m_irq_a1; |