Electronic Components Datasheet Search |
|
COP87L88RW Datasheet(PDF) 7 Page - National Semiconductor (TI) |
|
|
COP87L88RW Datasheet(HTML) 7 Page - National Semiconductor (TI) |
7 / 42 page Data Memory Segment RAM Extension (Continued) The data store memory is either addressed directly by a single-byte address within the instruction or indirectly rela- tive to the reference of the B X or SP pointers (each con- tains a single-byte address) This single-byte address allows an addressing range of 256 locations from 00 to FF hex The upper bit of this single-byte address divides the data store memory into two separate sections as outlined previ- ously With the exception of the RAM register memory from address locations 00F0 to 00FF all RAM memory is memo- ry mapped with the upper bit of the single-byte address be- ing equal to zero This allows the upper bit of the single-byte address to determine whether or not the base address range (from 0000 to 00FF) is extended If this upper bit equals one (representing address range 0080 to 00FF) then address extension does not take place Alternatively if this upper bit equals zero then the data segment extension register S is used to extend the base address range (from 0000 to 007F) from XX00 to XX7F where XX represents the 8 bits from the S register Thus the 128-byte data segment extensions are located from addresses 0100 to 017F for data segment 1 0200 to 027F for data segment 2 etc up to FF00 to FF7F for data segment 255 The base address range from 0000 to 007F represents data segment 0 Figure 5 illustrates how the S register data memory exten- sion is used in extending the lower half of the base address range (00 to 7F hex) into 256 data segments of 128 bytes each with a total addressing range of 32 kbytes from XX00 to XX7F This organization allows a total of 256 data seg- ments of 128-bytes each with an additional upper base seg- ment of 128 bytes Furthermore all addressing modes are available for all data segments The S register must be changed under program control to move from one data seg- ment (128 bytes) to another However the upper base seg- ment (containing the 16 memory registers IO registers controI registers etc) is always available regardless of the contents of the S register since the upper base segment (address range 0080 to 00FF) is independent of data seg- ment extension The instructions that utilize the stack pointer (SP) always reference the stack as part of the base segment (Segment 0) regardless of the contents of the S register The S regis- ter is not changed by these instructions Consequently the stack (used with subroutine linkage and interrupts) is always located in the base segment The stack pointer will be initial- ized to point at data memory location 006F as a result of reset The 128 bytes of RAM contained in the base segment are split between the Iower and upper base segments The first 112 bytes of RAM are resident from address 0000 to 006F in the Iower base segment while the remaining 16 bytes of RAM represent the 16 data memory registers located at ad- dresses 00F0 to 00FF of the upper base segment No RAM is located at the upper sixteen addresses (0070 to 007F) of the lower base segment Additional RAM beyond these initial 128 bytes however will always be memory mapped in groups of 128 bytes (or less) at the data segment address extensions (XX00 to XX7F) of the lower base segment The additional 384 bytes of RAM in this device are memory mapped at address locations 0100 to 017F 0200 to 027F and 0300 to 037F hex TLDD12855 – 5 Reads as all ones FIGURE 5 RAM Organization http www nationalcom 7 |
Similar Part No. - COP87L88RW |
|
Similar Description - COP87L88RW |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |