`timescale 1ns / 100ps /* * Zilog 8530 SCC module for minimigmac. * * Located on high data bus, but writes are done at odd addresses as * LDS is used as WR signals or something like that on a Mac Plus. * * We don't care here and just ignore which side was used. * * NOTE: We don't implement the 85C30 or ESCC additions such as WR7' * for now, it's all very simplified */ module scc(input sysclk, input reset_hw, /* Bus interface. 2-bit address, to be wired * appropriately upstream (to A1..A2). */ input cs, input we, input [1:0] rs, /* [1] = data(1)/ctl [0] = a_side(1)/b_side */ input [7:0] wdata, output [7:0] rdata, output _irq, /* A single serial port on Minimig */ input rxd, output txd, input cts, /* normally wired to device DTR output * on Mac cables. That same line is also * connected to the TRxC input of the SCC * to do fast clocking but we don't do that * here */ output rts, /* on a real mac this activates line * drivers when low */ /* DCD for both ports are hijacked by mouse interface */ input dcd_a, /* We don't synchronize those inputs */ input dcd_b, /* Write request */ output wreq ); /* Register access is semi-insane */ reg [3:0] rindex; wire wreg_a; wire wreg_b; wire wdata_a; wire wdata_b; wire rdata_a; wire rdata_b; /* Resets via WR9, one clk pulses */ wire reset_a; wire reset_b; wire reset; /* Data registers */ reg [7:0] data_a; reg [7:0] data_b; /* Read registers */ wire [7:0] rr0_a; wire [7:0] rr0_b; wire [7:0] rr1_a; wire [7:0] rr1_b; wire [7:0] rr2_b; wire [7:0] rr3_a; wire [7:0] rr10_a; wire [7:0] rr10_b; wire [7:0] rr15_a; wire [7:0] rr15_b; /* Write registers. Only some are implemented, * some result in actions on write and don't * store anything */ reg [7:0] wr1_a; reg [7:0] wr1_b; reg [7:0] wr2; reg [7:0] wr3_a; reg [7:0] wr3_b; reg [7:0] wr4_a; reg [7:0] wr4_b; reg [7:0] wr5_a; reg [7:0] wr5_b; reg [7:0] wr6_a; reg [7:0] wr6_b; reg [7:0] wr7_a; reg [7:0] wr7_b; reg [7:0] wr8_a; reg [7:0] wr8_b; reg [5:0] wr9; reg [7:0] wr10_a; reg [7:0] wr10_b; reg [7:0] wr11_a; reg [7:0] wr11_b; reg [7:0] wr12_a; reg [7:0] wr12_b; reg [7:0] wr13_a; reg [7:0] wr13_b; reg [7:0] wr14_a; reg [7:0] wr14_b; reg [7:0] wr15_a; reg [7:0] wr15_b; /* Status latches */ reg latch_open_a; reg latch_open_b; reg dcd_latch_a; reg dcd_latch_b; wire dcd_ip_a; wire dcd_ip_b; wire do_latch_a; wire do_latch_b; wire do_extreset_a; wire do_extreset_b; /* IRQ stuff */ wire rx_irq_pend_a; wire rx_irq_pend_b; wire tx_irq_pend_a; wire tx_irq_pend_b; wire ex_irq_pend_a; wire ex_irq_pend_b; reg ex_irq_ip_a; reg ex_irq_ip_b; wire [2:0] rr2_vec_stat; /* Register/Data access helpers */ assign wreg_a = cs & we & (~rs[1]) & rs[0]; assign wreg_b = cs & we & (~rs[1]) & ~rs[0]; assign wdata_a = cs & we & (rs[1] | (rindex == 8)) & rs[0]; assign wdata_b = cs & we & (rs[1] | (rindex == 8)) & ~rs[0]; assign rdata_a = cs & (~we) & (rs[1] | (rindex == 8)) & rs[0]; assign rdata_b = cs & (~we) & (rs[1] | (rindex == 8)) & ~rs[0]; /* Register index is set by a write to WR0 and reset * after any subsequent write. We ignore the side */ always@(posedge sysclk or posedge reset) begin if (reset) rindex <= 0; else if (cs && !rs[1]) begin /* Default, reset index */ rindex <= 0; /* Write to WR0 */ if (we && rindex == 0) begin /* Get low index bits */ rindex[2:0] <= wdata[2:0]; /* Add point high */ rindex[3] <= (wdata[5:3] == 3'b001); end end end /* Reset logic (write to WR9 cmd) * * Note about resets: Some bits are documented as unchanged/undefined on * HW reset by the doc. We apply this to channel and soft resets, however * we _do_ reset every bit on an external HW reset in this implementation * to make the FPGA & synthesis tools happy. */ assign reset = ((wreg_a | wreg_b) & (rindex == 9) & (wdata[7:6] == 2'b11)) | reset_hw; assign reset_a = ((wreg_a | wreg_b) & (rindex == 9) & (wdata[7:6] == 2'b10)) | reset; assign reset_b = ((wreg_a | wreg_b) & (rindex == 9) & (wdata[7:6] == 2'b01)) | reset; /* WR1 * Reset: bit 5 and 2 unchanged */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr1_a <= 0; else begin if (reset_a) wr1_a <= { 2'b00, wr1_a[5], 2'b00, wr1_a[2], 2'b00 }; else if (wreg_a && rindex == 1) wr1_a <= wdata; end end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr1_b <= 0; else begin if (reset_b) wr1_b <= { 2'b00, wr1_b[5], 2'b00, wr1_b[2], 2'b00 }; else if (wreg_b && rindex == 1) wr1_b <= wdata; end end /* WR2 * Reset: unchanged */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr2 <= 0; else if ((wreg_a || wreg_b) && rindex == 2) wr2 <= wdata; end /* WR3 * Reset: bit 0 to 0, otherwise unchanged. */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr3_a <= 0; else begin if (reset_a) wr3_a[0] <= 0; else if (wreg_a && rindex == 3) wr3_a <= wdata; end end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr3_b <= 0; else begin if (reset_b) wr3_b[0] <= 0; else if (wreg_b && rindex == 3) wr3_b <= wdata; end end /* WR4 * Reset: Bit 2 to 1, otherwise unchanged */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr4_a <= 0; else begin if (reset_a) wr4_a[2] <= 1; else if (wreg_a && rindex == 4) wr4_a <= wdata; end end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr4_b <= 0; else begin if (reset_b) wr4_b[2] <= 1; else if (wreg_b && rindex == 4) wr4_b <= wdata; end end /* WR5 * Reset: Bits 7,4,3,2,1 to 0 */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr5_a <= 0; else begin if (reset_a) wr5_a <= { 1'b0, wr5_a[6:5], 4'b0000, wr5_a[0] }; else if (wreg_a && rindex == 5) wr5_a <= wdata; end end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr5_b <= 0; else begin if (reset_b) wr5_b <= { 1'b0, wr5_b[6:5], 4'b0000, wr5_b[0] }; else if (wreg_b && rindex == 5) wr5_b <= wdata; end end /* WR6 * Reset: Unchanged. */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr6_a <= 0; else if (wreg_a && rindex == 6) wr6_a <= wdata; end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr6_b <= 0; else if (wreg_b && rindex == 6) wr6_b <= wdata; end /* WR7 * Reset: Unchanged. */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr7_a <= 0; else if (wreg_a && rindex == 7) wr7_a <= wdata; end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr7_b <= 0; else if (wreg_b && rindex == 7) wr7_b <= wdata; end /* WR9. Special: top bits are reset, handled separately, bottom * bits are only reset by a hw reset */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr9 <= 0; else if ((wreg_a || wreg_b) && rindex == 9) wr9 <= wdata[5:0]; end /* WR10 * Reset: all 0, except chanel reset retains 6 and 5 */ always@(posedge sysclk or posedge reset) begin if (reset) wr10_a <= 0; else begin if (reset_a) wr10_a <= { 1'b0, wr10_a[6:5], 5'b00000 }; else if (wreg_a && rindex == 10) wr10_a <= wdata; end end always@(posedge sysclk or posedge reset) begin if (reset) wr10_b <= 0; else begin if (reset_b) wr10_b <= { 1'b0, wr10_b[6:5], 5'b00000 }; else if (wreg_b && rindex == 10) wr10_b <= wdata; end end /* WR11 * Reset: On full reset only, not channel reset */ always@(posedge sysclk or posedge reset) begin if (reset) wr11_a <= 8'b00001000; else if (wreg_a && rindex == 11) wr11_a <= wdata; end always@(posedge sysclk or posedge reset) begin if (reset) wr11_b <= 8'b00001000; else if (wreg_b && rindex == 11) wr11_b <= wdata; end /* WR12 * Reset: Unchanged */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr12_a <= 0; else if (wreg_a && rindex == 12) wr12_a <= wdata; end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr12_b <= 0; else if (wreg_b && rindex == 12) wr12_b <= wdata; end /* WR13 * Reset: Unchanged */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr13_a <= 0; else if (wreg_a && rindex == 13) wr13_a <= wdata; end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr13_b <= 0; else if (wreg_b && rindex == 13) wr13_b <= wdata; end /* WR14 * Reset: Full reset maintains top 2 bits, * Chan reset also maitains bottom 2 bits, bit 4 also * reset to a different value */ always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr14_a <= 0; else begin if (reset) wr14_a <= { wr14_a[7:6], 6'b110000 }; else if (reset_a) wr14_a <= { wr14_a[7:6], 4'b1000, wr14_a[1:0] }; else if (wreg_a && rindex == 14) wr14_a <= wdata; end end always@(posedge sysclk or posedge reset_hw) begin if (reset_hw) wr14_b <= 0; else begin if (reset) wr14_b <= { wr14_b[7:6], 6'b110000 }; else if (reset_b) wr14_b <= { wr14_b[7:6], 4'b1000, wr14_b[1:0] }; else if (wreg_b && rindex == 14) wr14_b <= wdata; end end /* WR15 */ always@(posedge sysclk or posedge reset) begin if (reset) wr15_a <= 8'b11111000; else if (wreg_a && rindex == 15) wr15_a <= wdata; end always@(posedge sysclk or posedge reset) begin if (reset) wr15_b <= 8'b11111000; else if (wreg_b && rindex == 15) wr15_b <= wdata; end /* Read data mux */ assign rdata = rs[1] && rs[0] ? data_a : rs[1] ? data_b : rindex == 0 && rs[0] ? rr0_a : rindex == 0 ? rr0_b : rindex == 1 && rs[0] ? rr1_a : rindex == 1 ? rr1_b : rindex == 2 && rs[0] ? wr2 : rindex == 2 ? rr2_b : rindex == 3 && rs[0] ? rr3_a : rindex == 3 ? 0 : rindex == 4 && rs[0] ? rr0_a : rindex == 4 ? rr0_b : rindex == 5 && rs[0] ? rr1_a : rindex == 5 ? rr1_b : rindex == 6 && rs[0] ? wr2 : rindex == 6 ? rr2_b : rindex == 7 && rs[0] ? rr3_a : rindex == 7 ? 0 : rindex == 8 && rs[0] ? data_a : rindex == 8 ? data_b : rindex == 9 && rs[0] ? wr13_a : rindex == 9 ? wr13_b : rindex == 10 && rs[0] ? rr10_a : rindex == 10 ? rr10_b : rindex == 11 && rs[0] ? rr15_a : rindex == 11 ? rr15_b : rindex == 12 && rs[0] ? wr12_a : rindex == 12 ? wr12_b : rindex == 13 && rs[0] ? wr13_a : rindex == 13 ? wr13_b : rindex == 14 && rs[0] ? rr10_a : rindex == 14 ? rr10_b : rindex == 15 && rs[0] ? rr15_a : rindex == 15 ? rr15_b : 8'hff; /* RR0 */ assign rr0_a = { 1'b0, /* Break */ 1'b1, /* Tx Underrun/EOM */ 1'b0, /* CTS */ 1'b0, /* Sync/Hunt */ wr15_a[3] ? dcd_latch_a : dcd_a, /* DCD */ 1'b1, /* Tx Empty */ 1'b0, /* Zero Count */ 1'b0 /* Rx Available */ }; assign rr0_b = { 1'b0, /* Break */ 1'b1, /* Tx Underrun/EOM */ 1'b0, /* CTS */ 1'b0, /* Sync/Hunt */ wr15_b[3] ? dcd_latch_b : dcd_b, /* DCD */ 1'b1, /* Tx Empty */ 1'b0, /* Zero Count */ 1'b0 /* Rx Available */ }; /* RR1 */ assign rr1_a = { 1'b0, /* End of frame */ 1'b0, /* CRC/Framing error */ 1'b0, /* Rx Overrun error */ 1'b0, /* Parity error */ 1'b0, /* Residue code 0 */ 1'b1, /* Residue code 1 */ 1'b1, /* Residue code 2 */ 1'b1 /* All sent */ }; assign rr1_b = { 1'b0, /* End of frame */ 1'b0, /* CRC/Framing error */ 1'b0, /* Rx Overrun error */ 1'b0, /* Parity error */ 1'b0, /* Residue code 0 */ 1'b1, /* Residue code 1 */ 1'b1, /* Residue code 2 */ 1'b1 /* All sent */ }; /* RR2 (Chan B only, A is just WR2) */ assign rr2_b = { wr2[7], wr9[4] ? rr2_vec_stat[0] : wr2[6], wr9[4] ? rr2_vec_stat[1] : wr2[5], wr9[4] ? rr2_vec_stat[2] : wr2[4], wr9[4] ? wr2[3] : rr2_vec_stat[2], wr9[4] ? wr2[2] : rr2_vec_stat[1], wr9[4] ? wr2[1] : rr2_vec_stat[0], wr2[0] }; /* RR3 (Chan A only) */ assign rr3_a = { 2'b0, rx_irq_pend_a, /* Rx interrupt pending */ tx_irq_pend_a, /* Tx interrupt pending */ ex_irq_pend_a, /* Status/Ext interrupt pending */ rx_irq_pend_b, tx_irq_pend_b, ex_irq_pend_b }; /* RR10 */ assign rr10_a = { 1'b0, /* One clock missing */ 1'b0, /* Two clocks missing */ 1'b0, 1'b0, /* Loop sending */ 1'b0, 1'b0, 1'b0, /* On Loop */ 1'b0 }; assign rr10_b = { 1'b0, /* One clock missing */ 1'b0, /* Two clocks missing */ 1'b0, 1'b0, /* Loop sending */ 1'b0, 1'b0, 1'b0, /* On Loop */ 1'b0 }; /* RR15 */ assign rr15_a = { wr15_a[7], wr15_a[6], wr15_a[5], wr15_a[4], wr15_a[3], 1'b0, wr15_a[1], 1'b0 }; assign rr15_b = { wr15_b[7], wr15_b[6], wr15_b[5], wr15_b[4], wr15_b[3], 1'b0, wr15_b[1], 1'b0 }; /* Interrupts. Simplified for now * * Need to add latches. Tx irq is latched when buffer goes from full->empty, * it's not a permanent state. For now keep it clear. Will have to fix that. */ assign rx_irq_pend_a = 0; assign tx_irq_pend_a = 0 /*& wr1_a[1]*/; /* Tx always empty for now */ assign ex_irq_pend_a = ex_irq_ip_a; assign rx_irq_pend_b = 0; assign tx_irq_pend_b = 0 /*& wr1_b[1]*/; /* Tx always empty for now */ assign ex_irq_pend_b = ex_irq_ip_b; assign _irq = ~(wr9[3] & (rx_irq_pend_a | rx_irq_pend_b | tx_irq_pend_a | tx_irq_pend_b | ex_irq_pend_a | ex_irq_pend_b)); /* XXX Verify that... also missing special receive condition */ assign rr2_vec_stat = rx_irq_pend_a ? 3'b110 : tx_irq_pend_a ? 3'b100 : ex_irq_pend_a ? 3'b101 : rx_irq_pend_b ? 3'b010 : tx_irq_pend_b ? 3'b000 : ex_irq_pend_b ? 3'b001 : 3'b011; /* External/Status interrupt & latch logic */ assign do_extreset_a = wreg_a & (rindex == 0) & (wdata[5:3] == 3'b010); assign do_extreset_b = wreg_b & (rindex == 0) & (wdata[5:3] == 3'b010); /* Internal IP bit set if latch different from source and * corresponding interrupt is enabled in WR15 */ assign dcd_ip_a = (dcd_a != dcd_latch_a) & wr15_a[3]; assign dcd_ip_b = (dcd_b != dcd_latch_b) & wr15_b[3]; /* Latches close when an enabled IP bit is set and latches * are currently open */ assign do_latch_a = latch_open_a & (dcd_ip_a /* | cts... */); assign do_latch_b = latch_open_b & (dcd_ip_b /* | cts... */); /* "Master" interrupt, set when latch close & WR1[0] is set */ always@(posedge sysclk or posedge reset) begin if (reset) ex_irq_ip_a <= 0; else if (do_extreset_a) ex_irq_ip_a <= 0; else if (do_latch_a && wr1_a[0]) ex_irq_ip_a <= 1; end always@(posedge sysclk or posedge reset) begin if (reset) ex_irq_ip_b <= 0; else if (do_extreset_b) ex_irq_ip_b <= 0; else if (do_latch_b && wr1_b[0]) ex_irq_ip_b <= 1; end /* Latch open/close control */ always@(posedge sysclk or posedge reset) begin if (reset) latch_open_a <= 1; else begin if (do_extreset_a) latch_open_a <= 1; else if (do_latch_a) latch_open_a <= 0; end end always@(posedge sysclk or posedge reset) begin if (reset) latch_open_b <= 1; else begin if (do_extreset_b) latch_open_b <= 1; else if (do_latch_b) latch_open_b <= 0; end end /* Latches proper */ always@(posedge sysclk or posedge reset) begin if (reset) begin dcd_latch_a <= 0; /* cts ... */ end else begin if (do_latch_a) dcd_latch_a <= dcd_a; /* cts ... */ end end always@(posedge sysclk or posedge reset) begin if (reset) begin dcd_latch_b <= 0; /* cts ... */ end else begin if (do_latch_b) dcd_latch_b <= dcd_b; /* cts ... */ end end /* NYI */ assign txd = 1; assign rts = 1; assign wreq = 0; endmodule