PCM18XT0 Microchip Technology, PCM18XT0 Datasheet - Page 100

• Manufacturer Part Number: PCM18XT0
• Description: MODULE PROC PIC18F4685
• Manufacturer: Microchip Technology

Specifications of PCM18XT0

• Accessory Type: Processor Module
• Product: Microcontroller Modules
• Core Processor: PIC18F4685
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: ICE2000
• For Use With: ICE2000 - EMULATOR MPLAB-ICE 2000 POD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

PIC18F2682/2685/4682/4685
6.2.2
The Table Latch (TABLAT) is an 8-bit register mapped
into the SFR space. The Table Latch register is used to
hold 8-bit data during data transfers between program
memory and data RAM.
6.2.3
The Table Pointer (TBLPTR) register addresses a byte
within the program memory. The TBLPTR is comprised
of three SFR registers: Table Pointer Upper Byte, Table
Pointer High Byte and Table Pointer Low Byte
(TBLPTRU:TBLPTRH:TBLPTRL). These three regis-
ters join to form a 22-bit wide pointer. The low-order
21 bits allow the device to address up to 2 Mbytes of
program memory space. The 22nd bit allows access to
the Device ID, the user ID and the Configuration bits.
The Table Pointer, TBLPTR, is used by the TBLRD and
TBLWT instructions. These instructions can update the
TBLPTR in one of four ways based on the table opera-
tion. These operations are shown in Table 6-1. These
operations on the TBLPTR only affect the low-order
21 bits.
TABLE 6-1:
FIGURE 6-3:
DS39761C-page 100
TBLRD*
TBLWT*
TBLRD*+
TBLWT*+
TBLRD*-
TBLWT*-
TBLRD+*
TBLWT+*
Example
21
TABLAT – TABLE LATCH REGISTER
TBLPTR – TABLE POINTER
REGISTER
TBLPTRU
TABLE POINTER OPERATIONS WITH TBLRD AND TBLWT INSTRUCTIONS
TABLE POINTER BOUNDARIES BASED ON OPERATION
16
15
Table Erase/Write
TBLPTR<21:6>
TBLPTR is incremented before the read/write
Table Read – TBLPTR<21:0>
TBLPTR is decremented after the read/write
TBLPTR is incremented after the read/write
TBLPTRH
Operation on Table Pointer
TBLPTR is not modified
6.2.4
TBLPTR is used in reads, writes and erases of the
Flash program memory.
When a TBLRD is executed, all 22 bits of the TBLPTR
determine which byte is read from program memory
into TABLAT.
When a TBLWT is executed, the six LSbs of the Table
Pointer register (TBLPTR<5:0>) determine which of the
64 program memory holding registers is written to.
When the timed write to program memory begins (via
the WR bit), the 16 MSbs of the TBLPTR
(TBLPTR<21:6>) determine which program memory
block of 64 bytes is written to. For more detail, see
Section 6.5 “Writing to Flash Program Memory”.
When an erase of program memory is executed, the
16 MSbs of the Table Pointer register (TBLPTR<21:6>)
point to the 64-byte block that will be erased. The Least
Significant bits (TBLPTR<5:0>) are ignored.
Figure 6-3 describes the relevant boundaries of
TBLPTR based on Flash program memory operations.
8
TABLE POINTER BOUNDARIES
7
TBLPTRL
© 2009 Microchip Technology Inc.
TBLPTR<5:0>
Table Write
0