X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/30364d271166fd7359ff88d4b4fc22d63395ed9d..8b5ec1f4a68e86ae1bffe965d3e131ad709b75fc:/fpga/hi_iso14443a.v?ds=sidebyside diff --git a/fpga/hi_iso14443a.v b/fpga/hi_iso14443a.v index ccb51d8f..b1b7b141 100644 --- a/fpga/hi_iso14443a.v +++ b/fpga/hi_iso14443a.v @@ -311,9 +311,13 @@ reg [3:0] sub_carrier_cnt; // The ARM must not send too early, otherwise the mod_sig_buf will overflow, therefore signal that we are ready // with fdt_indicator. The mod_sig_buf can buffer 29 excess data bits, i.e. a maximum delay of 29 * 16 = 464 adc_clk ticks. -// fdt_indicator could appear at ssp_din after 1 tick, the transfer needs 16 ticks, the ARM can send 128 ticks later. -// 1128 - 464 - 1 - 128 - 8 = 535 -`define FDT_INDICATOR_COUNT 11'd535 +// fdt_indicator is assigned to sendbit after at least 1 tick, the transfer to ARM needs minimum 8 ticks. Response from +// ARM could appear at ssp_dout 8 ticks later. +// 1128 - 464 - 1 - 8 - 8 = 647 +`define FDT_INDICATOR_COUNT 11'd647 +// Note: worst case, assignment to sendbit takes 15 ticks more, and transfer to ARM needs 7*16 = 112 ticks more. +// When the ARM's response then appears, the fdt_count is already 647 + 15 + 112 = 774, which still allows the ARM a possible +// response window of 1128 - 774 = 354 ticks. // reset on a pause in listen mode. I.e. the counter starts when the pause is over: assign fdt_reset = ~after_hysteresis && mod_type == `TAGSIM_LISTEN;