static void tsc2102_control_register_write(
                TSC210xState *s, int reg, uint16_t value)
{
    switch (reg) {
    case 0x00:	/* TSC ADC */
        s->host_mode = value >> 15;
        s->enabled = !(value & 0x4000);
        if (s->busy && !s->enabled)
            timer_del(s->timer);
        s->busy &= s->enabled;
        s->nextfunction = (value >> 10) & 0xf;
        s->nextprecision = (value >> 8) & 3;
        s->filter = value & 0xff;
        return;

    case 0x01:	/* Status / Keypad Control */
        if ((s->model & 0xff00) == 0x2100)
            s->pin_func = value >> 14;
	else {
            s->kb.scan = (value >> 14) & 1;
            s->kb.debounce = (value >> 11) & 7;
            if (s->kb.intr && s->kb.scan) {
                s->kb.intr = 0;
                qemu_irq_raise(s->kbint);
            }
        }
        return;

    case 0x02:	/* DAC Control */
        if ((s->model & 0xff00) == 0x2300) {
            s->dac_power &= 0x7fff;
            s->dac_power |= 0x8000 & value;
        } else
            goto bad_reg;
        break;

    case 0x03:	/* Reference */
        s->ref = value & 0x1f;
        return;

    case 0x04:	/* Reset */
        if (value == 0xbb00) {
            if (s->busy)
                timer_del(s->timer);
            tsc210x_reset(s);
#ifdef TSC_VERBOSE
        } else {
            fprintf(stderr, "tsc2102_control_register_write: "
                            "wrong value written into RESET\n");
#endif
        }
        return;

    case 0x05:	/* Configuration */
        s->timing = value & 0x3f;
#ifdef TSC_VERBOSE
        if (value & ~0x3f)
            fprintf(stderr, "tsc2102_control_register_write: "
                            "wrong value written into CONFIG\n");
#endif
        return;

    case 0x06:	/* Secondary configuration */
        if ((s->model & 0xff00) == 0x2100)
            goto bad_reg;
        s->kb.mode = value >> 14;
        s->pll[2] = value & 0x3ffff;
        return;

    case 0x10:	/* Keypad Mask */
        if ((s->model & 0xff00) == 0x2100)
            goto bad_reg;
        s->kb.mask = value;
        return;

    default:
    bad_reg:
#ifdef TSC_VERBOSE
        fprintf(stderr, "tsc2102_control_register_write: "
                        "no such register: 0x%02x\n", reg);
#endif
    }
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.