Makes accesible a memory zone from the upper 64Kb on a standard CPC 6128 or from a memory extension.
void cpct_pageMemory (u8 configAndBankValue);
| (1B A) configAndBankValue | RAM pages configuration |
call cpct_pageMemory_asm
This function modifies the memory layout. The memory address is changed based on the current configuration, and depending on the configuration, extended memory can be accessed using 16 bit addresses. Due to the address bus size, the address only represents 64Kb of data. In order to use memory higher than the first 64Kb, memory must be “paged-in”. The process of paging the memory can also be used to alter the order of the pages, whether in the first 64Kb of data or higher.
Memory layout is defined by: The RAM pages configuration and the memory bank we will use to page. There are 8 possible RAM configurations, shown below:
-Address- 0 1 2 3 4 5 6 7 0000-3FFF RAM_0 RAM_0 RAM_4 RAM_0 RAM_0 RAM_0 RAM_0 RAM_0 4000-7FFF RAM_1 RAM_1 RAM_5 RAM_3 RAM_4 RAM_5 RAM_6 RAM_7 8000-BFFF RAM_2 RAM_2 RAM_6 RAM_2 RAM_2 RAM_2 RAM_2 RAM_2 C000-FFFF RAM_3 RAM_7 RAM_7 RAM_7 RAM_3 RAM_3 RAM_3 RAM_3
Default configuration is the 0 config, where only the first 64Kb of memory are accessed.
The actual pages represented by RAM0-RAM7 depend on the bank number. The bank number is 0 for the first 64Kb in the expansion, 1 for the next 64Kb, and so on.
The Video RAM is always located in the first 64K, VRAM is in no way affected by this register.
For example, it is typical to bank using the 0x4000 memory address as target. In this scenario the configurations 0, 4, 5, 6 and 7 are used in conjunction with the BANK 0, which is the first 64 Kb of memory, because you want the selected RAM page to be loaded in the first 64Kb.
In order to easily use the banks, there are macro definitions available to use either in C or in assembly (see Memory Pagination Macros). For C users, they are directly available when one of these headers is included: cpctelera.h, memutils/banks.h. Assembly users may include memutils/cpct_setBank_const.asm.
AF, BC
L (when called through C-interface)
| C-binding | 9 bytes |
| ASM-binding | 8 bytes |
Case | microSecs (us) | CPU Cycles | ------------------------------------------- Any | 13 | 52 | ------------------------------------------- Asm saving | -1 | -4 | -------------------------------------------