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Adds notes on intended meaning of status register.

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This commit is contained in:
Thomas Harte 2021-06-21 07:31:58 -04:00
parent b49cc407c6
commit 117f9a9794
3 changed files with 33 additions and 12 deletions
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41
Machines/Enterprise/EXDos.cpp
View File

@ -17,12 +17,30 @@ EXDos::EXDos() : WD1770(P1770) {
void EXDos::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, size_t drive) {
get_drive(drive).set_disk(disk);
disk_did_change_ = true;
}
void EXDos::set_control_register(uint8_t control) {
printf("Control: %02x\n", control);
// Documentation for the control register:
//
// Write:
// b7 in use (???)
// b6 disk change reset
// b5 0 = double density, 1 = single density
// b4 side 1 select
// b3, b3, b1, b0 select drive 3, 2, 1, 0
//
// Read:
// b7 data request from WD1770
// b6 disk change
// b5, b4, b3, b2: not used
// b1 interrupt request from WD1770
// b0 drive ready
last_control_ = control;
void EXDos::set_control_register(uint8_t control) {
printf("Set control: %02x\n", control);
if(control & 0x40) disk_did_change_ = false;
set_is_double_density(!(control & 0x20));
// Set side.
const int head = (control >> 4) & 1;
@ -38,16 +56,19 @@ void EXDos::set_control_register(uint8_t control) {
set_drive(c);
}
}
// TODO: seems like bit 6 might be connected to the drive's RDY line?
// TODO: does part of this register select double/single density mode?
// Probably either bit 5 or bit 7 of the control register?
set_is_double_density(true);
}
uint8_t EXDos::get_control_register() {
return last_control_ | (get_drive().get_is_ready() ? 0x40 : 0x00);
// TODO: how does disk_did_change_ really work? Presumably
// it latches RDY?
const uint8_t status =
(get_data_request_line() ? 0x80 : 0x00) |
(disk_did_change_ ? 0x40 : 0x00) |
(get_interrupt_request_line() ? 0x02 : 0x00) |
(get_drive().get_is_ready() ? 0x01 : 0x00);
printf("Get status: %02x\n", status);
return status;
}
void EXDos::set_motor_on(bool on) {

2
Machines/Enterprise/EXDos.hpp
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@ -24,7 +24,7 @@ class EXDos final : public WD::WD1770 {
uint8_t get_control_register();
private:
uint8_t last_control_ = 0;
bool disk_did_change_ = false;
void set_motor_on(bool on) override;
};

2
Machines/Enterprise/Enterprise.cpp
View File

@ -287,7 +287,7 @@ template <bool has_disk_controller> class ConcreteMachine:
case 0xa4: case 0xa5: case 0xa6: case 0xa7:
case 0xa8: case 0xa9: case 0xaa: case 0xab:
case 0xac: case 0xad: case 0xae: case 0xaf:
printf("TODO: audio adjust %04x <- %02x\n", address, *cycle.value);
// printf("TODO: audio adjust %04x <- %02x\n", address, *cycle.value);
break;
case 0xb4: