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Enhanced TIMER App from MartinR

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- MartinR has enhanced the TIMER application to display output in decimal.
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Wayne Warthen
2024-06-30 11:53:38 -07:00
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@@ -126,6 +126,142 @@ execution.
![Bank Switched Memory Layout](Graphics/BankSwitchedMemory){ width=100% }
## Bank Id
RomWBW utilizes a specific assignment of memory banks for dedicated
purposes. A numeric Bank Id is used to refer to the memory banks. The
Bank Id is a single byte. In general, the Bank Id simply refers to each
of the 32K banks in sequential order. In other words, Bank Id 0 is the
first physical 32K, Bank Id 1 is the second, etc. However, the high
order bit of the Bank Id has a special meaning. If it is 0, it indicates
a ROM bank is being referred to. If it is 1, it indicates a RAM bank
is being referred to.
For example, let's say we have a typical system with 512KB of ROM and
512KB of RAM. The Bank Ids would look like this:
| Physical Memory | Type | Physical Bank | Bank Id |
|-------------------|------|---------------|-----------|
| 0x000000-0x007FFF | ROM | 0 | 0x00 |
| 0x008000-0x00FFFF | ROM | 1 | 0x01 |
| 0x010000-0x07FFFF | ROM | 2-15 | 0x02-0x0F |
| 0x080000-0x087FFF | RAM | 16 | 0x80 |
| 0x088000-0x08FFFF | RAM | 17 | 0x81 |
| 0x090000-0x0FFFFF | RAM | 18-31 | 0x82-0x8F |
Note that Bank Id 0x00 is **always** the first bank of ROM and 0x80 is
**always** the first bank of RAM. If there were more banks of physical ROM,
they would be assigned Bank Ids starting with 0x10. Likewise, additional
bank of physical RAM would be assigned Bank Ids starting with 0x90.
The Bank Id is used in all RomWBW API functions when referring to
the mapping of banks to the lower 32K bank area of the processor. In
this way, all RomWBW functions can refer to a generic Bank Id without
needing to understand how a specific hardware platform accesses the
physical memory areas. A single routine within the HBIOS is implemented
for each memory manager that maps Bank Ids to physical memory.
## Bank Assignments
RomWBW requires dedicated banks of memory for specific purposes. It
uses Bank Ids via an algorithm to make these assignments. The following
table describes the way the banks are assigned. The Typical column
shows the specific values that would be assigned for a common system
with 512KB of ROM and 512KB of RAM (nROM=16, nRAM=16).
| Bank Id | Identity | Typical | Purpose |
|-------------------|-----------|---------|------------------------------------------|
| 0x00 |BID_BOOT | 0x00 | Boot Bank (HBIOS image) |
| 0x01 |BID_IMG0 | 0x01 | Boot Loader, Monitor, ROM OSes, ROM Apps |
| 0x02 |BID_IMG1 | 0x02 | ROM Apps |
| 0x03 |BID_IMG2 | 0x03 | \<Reserved\> |
| 0x04 |BID_ROMD0 | 0x04 | First ROM Disk Bank |
| nROM - 1 | | 0x0F | Last ROM Disk Bank |
| 0x80 |BID_BIOS | 0x80 | HBIOS (working copy) |
| 0x81 |BID_RAMD0 | 0x81 | First RAM Disk Bank |
| 0x80 + nRAM - 8 | | 0x88 | Last RAM Disk Bank |
| 0x80 + nRAM - 7 |BID_APP0 | 0x89 | First Application Bank |
| 0x80 + nRAM - 5 | | 0x8B | Last Application Bank |
| 0x80 + nRAM - 4 |BID_BUF | 0x8C | OS Disk Buffers |
| 0x80 + nRAM - 3 |BID_AUX | 0x8D | OS Code Bank |
| 0x80 + nRAM - 2 |BID_USR | 0x8E | User Bank (CP/M TPA) |
| 0x80 + nRAM - 1 |BID_COM | 0x8F | Common Bank |
In this table, nROM and nRAM refer to the number of corresponding
ROM and RAM banks in the the system.
The contents of the banks referred to above are described in more detail
below:
Boot Bank:
: The Boot Bank receives control when a system is first powered
on. It contains a ROM (read-only) copy of the HBIOS. At boot, it does
minimal hardware initialization, then copies itself to the HBIOS bank
in RAM, then resumes execution from the RAM bank.
Boot Loader:
: The application that handles loading of ROM or Disk based applications
including operating systems. It copies itself to a RAM bank at the
start of it's execution.
Monitor:
: The application that implements the basic system monitor functions.
It copies itself to a RAM bank at the start of it's execution.
ROM OSes:
: Code images of CP/M 2.2 and Z-System which are copied to RAM and
executed when a ROM-based operating system is selected in the Boot
Loader.
ROM Applications:
: Various ROM-based application images such as BASIC, FORTH, etc. They
can be selected in the Boot Loader. The Boot Loader will copy the
application image to a RAM bank, then transfer control to it.
ROM Disk:
: A sequential series of banks assigned to provide the system ROM Disk
contents.
HBIOS:
: This bank hosts the running copy of the RomWBW HBIOS.
RAM Disk:
: A sequential series of banks assigned to provide the system RAM Disk.
Application Bank:
: A sequential series of banks that are available for use by applications
that wish to utilize banked memory.
OS Disk Buffers:
: This bank is used by CP/M 3 and ZPM3 for disk buffer storage.
OS Code Bank:
: This bank is used by CP/M 3 and ZPM3 as an alternate bank for code.
This allows these operating systems to make additional TPA space
available for applications.
User Bank:
: This is the default bank for applications to use. This includes the
traditional TPA space for CP/M.
Common Bank:
: This bank is mapped to the upper 32K of the processors memory space.
It is a fixed mapping that is never changed in normal RomWBW operation
hence the name "Common".
# System Boot Process
A multi-phase boot strategy is employed. This is necessary because at